Dissertations / Theses on the topic 'Dynamics'
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1
Kulich, Martin. "Dynamic Template Adjustment in Continuous Keystroke Dynamics." Master's thesis, Vysoké učení technické v Brně. Fakulta informačních technologií, 2015. http://www.nusl.cz/ntk/nusl-234927.
Abstract:
Dynamika úhozů kláves je jednou z behaviorálních biometrických charakteristik, kterou je možné použít pro průběžnou autentizaci uživatelů. Vzhledem k tomu, že styl psaní na klávesnici se v čase mění, je potřeba rovněž upravovat biometrickou šablonu. Tímto problémem se dosud, alespoň pokud je autorovi známo, žádná studie nezabývala. Tato diplomová práce se pokouší tuto mezeru zaplnit. S pomocí dat o časování úhozů od 22 dobrovolníků bylo otestováno několik technik klasifikace, zda je možné je upravit na online klasifikátory, zdokonalující se bez učitele. Výrazné zlepšení v rozpoznání útočníka bylo zaznamenáno u jednotřídového statistického klasifikátoru založeného na normované Euklidovské vzdálenosti, v průměru o 23,7 % proti původní verzi bez adaptace, zlepšení však bylo pozorováno u všech testovacích sad. Změna míry rozpoznání správného uživatele se oproti tomu různila, avšak stále zůstávala na přijatelných hodnotách.
2
Munz, Marton. "Computational studies of protein dynamics and dynamic similarity." Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:2fb76765-3e43-409b-aad3-b5202f4668b3.
Abstract:
At the time of writing this thesis, the complete genomes of more than 180 organisms have been sequenced and more than 80000 biological macromolecular structures are available in the Protein Data Bank (PDB). While the number of sequenced genomes and solved three-dimensional structures are rapidly increasing, the functional annotation of protein sequences and structures is a much slower process, mostly because the experimental de-termination of protein function is expensive and time-consuming. A major class of in silico methods used for protein function prediction aim to transfer annotations between proteins based on sequence or structural similarities. These approaches rely on the assumption that homologous proteins of similar primary sequences and three-dimensional structures also have similar functions. While in most cases this assumption appears to be valid, an increasing number of examples show that proteins of highly similar sequences and/or structures can have different biochemical functions. Thus the relationship between the divergence of protein sequence, structure and function is more complex than previously anticipated. On the other hand, there is mounting evidence suggesting that minor changes of the sequences and structures of proteins can cause large differences in their conformational dynamics. As the intrinsic fluctuations of many proteins are key to their biochemical functions, the fact that very similar (almost identical) sequences or structures can have entirely different dynamics might be important for understanding the link between sequence, structure and function. In other words, the dynamic similarity of proteins could often serve as a better indicator of functional similarity than the similarity of their sequences or structures alone. Currently, little is known about how proteins are distributed in the 'dynamics space' and how protein motions depend on structure and sequence. These problems are relevant in the field of protein design, studying protein evolution and to better understand the functional differences of proteins. To address these questions, one needs a precise definition of dynamic similarity, which is not trivial given the complexity of protein motions. This thesis is intended to explore the possibilities of describing the similarity of proteins in the 'dynamics space'. To this end, novel methods of characterizing and comparing protein motions based on molecular dynamics simulation data were introduced. The generally applicable approach was tested on the family of PDZ domains; these small protein-protein interaction domains play key roles in many signalling pathways. The methodology was successfully used to characterize the dynamic dissimilarities of PDZ domains and helped to explain differences of their functional properties (e.g. binding promiscuity) also relevant for drug design studies. The software tools developed to implement the analysis are also introduced in the thesis. Finally, a network analysis study is presented to reveal dynamics-mediated intramolecular signalling pathways in an allosteric PDZ domain.
3
Zivanovic, Sanja. "Attractors in Dynamics with Choice." Scholarly Repository, 2009. http://scholarlyrepository.miami.edu/oa_dissertations/210.
Abstract:
Dynamics with choice is a generalization of discrete-time dynamics where instead of the same evolution operator at every time step there is a choice of operators to transform the current state of the system. Many real life processes studied in chemical physics, engineering, biology and medicine, from autocatalytic reaction systems to switched systems to cellular biochemical processes to malaria transmission in urban environments, exhibit the properties described by dynamics with choice. We study the long-term behavior in dynamics with choice. We prove very general results on the existence and properties of global compact attractors in dynamics with choice. In addition, we study the dynamics with restricted choice when the allowed sequences of operators correspond to subshifts of the full shift. One of practical consequences of our results is that when the parameters of a discrete-time system are not known exactly and/or are subject to change due to internal instability, or a strategy, or Nature's intervention, the long term behavior of the system may not be correctly described by a system with "averaged" values for the parameters. There may be a Gestalt effect.
4
Demiray, Turhan Hilmi. "Simulation of power system dynamics using dynamic phasor models /." Zürich : ETH, 2008. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=17607.
5
Durazzo, Gerardo. "Simulation of supply chains dynamics using fluid-dynamic models." Doctoral thesis, Universita degli studi di Salerno, 2013. http://hdl.handle.net/10556/887.
Abstract:
2011 - 2012The aim of thesis is to present some macroscopic models for supply chains and networks able to reproduce the goods dynamics, successively to show, via simulations, some phenomena appearing in planning and managing such systems and, finally, to dead with optimization problems... [edited by author]
XI n.s.
6
Kovář, Jiří. "Využití „Open Dynamics Engine“ pro modelování mobilních robotů." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2008. http://www.nusl.cz/ntk/nusl-227991.
Abstract:
This diploma thesis deals with the problems of virtual physical modelling of mobile robots for the needs of their real-time control. To create a virtual physical world, an open-source project OPEN DYNAMICS ENGINE (ODE) was used, the results were displayed facilitating DirectX graphical interface. Simulated systems in ODE were written in C# on Microsoft.NET platform. The properites and qualities in ODE were verified by simulation in several types of simple systems and on a simplified robot model "Kracmera I.". Subsequently, the usability of ODE for its control was being verified.
7
Mulder, William Alexander. "Dynamics of gas in a rotating galaxy." [Leiden] : Sterrewacht Leiden, 1985. http://catalog.hathitrust.org/api/volumes/oclc/12129828.html.
8
Marketing, Corporate Affairs and. "Dynamics." Corporate Affairs and Marketing, 2004. http://encore.tut.ac.za/iii/cpro/DigitalItemViewPage.external?sp=1000612.
9
Gotte, Anders. "Dynamics in Ceria and Related Materials from Molecular Dynamics and Lattice Dynamics." Doctoral thesis, Uppsala University, Department of Materials Chemistry, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-7374.
Abstract:
In discussions of heterogeneous catalysis and other surface-related phenomena, the dynamical properties of the catalytic material are often neglected, even at elevated temperatures. An example is the three-way catalyst (TWC), used for treatment of exhaust gases from combustion engines operating at several hundred degrees Celsius. In the TWC, reduced ceria (CeO2-x) is one of the key components, where it functions as an oxygen buffer, storing and releasing oxygen to provide optimal conditions for the catalytic conversion of the pollutants. In this process it is evident that dynamics plays a crucial role, not only ionic vibrations, but also oxygen diffusion.
In this thesis, the structure and dynamics of several ionic crystalline compounds and their surfaces have been studied by means of Molecular dynamics (MD) simulations and Lattice dynamics (LD) calculations. The main focus lies on CeO2-x, but also CeO2, MgO and CaF2 have been investigated.
The presence of oxygen vacancies in ceria is found to lead to significant distortions of the oxygen framework around the defect (but not of the cerium framework). As a consequence, a new O-O distance emerges, as well as a significantly broadened Ce-O distance distribution.
The presence of oxygen vacancies in ceria also leads to increased dynamics. The oxygen self-diffusion in reduced ceria was calculated from MD simulations in the temperature range 800-2000 K, and was found to follow an Arrhenius behaviour with a vacancy mechanism along the crystallographic <100> directions only.
The cation and anion vibrational surface dynamics were investigated for MgO (001) using DFT-LD and for CaF2 (111) in a combined LEED and MD study. Specific surface modes were found for MgO and increased surface dynamics was found both experimentally and theoretically for CaF2, which is isostructural with CeO2.
Many methodological aspects of modeling dynamics in ionic solids are also covered in this thesis. In many cases, the representation of the model system (slab thickness, simulation box-size and the choice of ensemble) was found to have a significant influence on the results.
10
Van, Wychen Wesley. "The Dynamics and Dynamic Discharge of the Ice Masses and Tidewater Glaciers of the Canadian High Arctic." Thesis, Université d'Ottawa / University of Ottawa, 2015. http://hdl.handle.net/10393/33180.
Abstract:
Speckle tracking of synthetic aperture RADAR imagery (Radarsat-1/2, ALOS PALSAR) and feature tracking of optical (Landsat-7 ETM+) imagery is used to determine the entire surface velocity structure of the major ice masses of the Canadian High Arctic in 2000, 2010-2015 and for select tidewater terminating glaciers from 1999-2010. At the termini of tidewater glaciers, surface ice velocities are combined with measured/modelled ice thicknesses to derive an estimate of mass loss via dynamic (iceberg) discharge. The total dynamic discharge for the ice masses of the southern Canadian Arctic Archipelago (SCAA: Baffin and Bylot Islands) is between ~17 and 180 Mt a-1 (0.017 to 0.180 Gt a-1) for the period 2007-2011, compared to a dynamic discharge of ~2.47 ± 0.88 Gt a-1 for the northern Canadian Arctic Archipelago (NCAA: Devon, Ellesmere, Axel Heiberg Islands) for the period 2011-2015. A comparison of these values with rates of mass loss via climatic mass balance (surface melt and runoff) indicates that dynamic discharge accounted for ~3.1% of total ablation for the NCAA in 2012 and ~0.11% of total ablation in the SCAA between 2007 and 2010. This reveals that total ablation in the Canadian Arctic is currently dominated by surface melt and runoff.
The glacier velocity dataset provides the most comprehensive record of ice motion and dynamic discharge in the Canadian Arctic to date and reveals a large degree of variability in glacier motion within the region over the last ~15 years. Most of the major glaciers in the NCAA have decelerated and their resultant dynamic discharge has decreased over the observation period, which is largely attributed to cyclical phases attributed to surging and pulsing. On pulse-type glaciers, variation in ice motion is largely confined to regions where the bed is located below sea level. A notable departure from the overall trend of regional velocity slowdown is the widespread acceleration of the Trinity and Wykeham Glaciers of the Prince of Wales Icefield (the largest glacier complex in the Canadian Arctic), which cannot be explained by surge or pulse mechanisms. The increased discharge from these two glaciers nearly compensates (within error) for the decrease in iceberg discharge from other glaciers across the study region and indicates that total dynamic discharge from the Canadian Arctic can be sensitive to the variations of ice flow of just a few glaciers.
11
Fujiwara, Naoya. "Dynamic phase transition and pattern dynamics in periodic external fields." 京都大学 (Kyoto University), 2007. http://hdl.handle.net/2433/135964.
12
Chen, C. C. "Imaging the spatial-temporal neuronal dynamics using dynamic causal modelling." Thesis, University College London (University of London), 2009. http://discovery.ucl.ac.uk/18517/.
Abstract:
Oscillatory brain activity is a ubiquitous feature of neuronal dynamics and the synchronous discharge of neurons is believed to facilitate integration both within functionally segregated brain areas and between areas engaged by the same task. There is growing interest in investigating the neural oscillatory networks in vivo. The aims of this thesis are to (1) develop an advanced method, Dynamic Causal Modelling for Induced Responses (DCM for IR), for modelling the brain network functions and (2) apply it to exploit the nonlinear coupling in the motor system during hand grips and the functional asymmetries during face perception. DCM for IR models the time-varying power over a range of frequencies of coupled electromagnetic sources. The model parameters encode coupling strength among areas and allows the differentiations between linear (within frequency) and nonlinear (between-frequency) coupling. I applied DCM for IR to show that, during hand grips, the nonlinear interactions among neuronal sources in motor system are essential while intrinsic coupling (within source) is very likely to be linear. Furthermore, the normal aging process alters both the network architecture and the frequency contents in the motor network. I then use the bilinear form of DCM for IR to model the experimental manipulations as the modulatory effects. I use MEG data to demonstrate functional asymmetries between forward and backward connections during face perception: Specifically, high (gamma) frequencies in higher cortical areas suppressed low (alpha) frequencies in lower areas. This finding provides direct evidence for functional asymmetries that is consistent with anatomical and physiological evidence from animal studies. Lastly, I generalize the bilinear form of DCM for IR to dissociate the induced responses from evoked ones in terms of their functional role. The backward modulatory effect is expressed as induced, but not evoked responses.
13
Da, Ronch Andrea. "On the calculation of dynamic derivatives using computational fluid dynamics." Thesis, University of Liverpool, 2012. http://livrepository.liverpool.ac.uk/5513/.
Abstract:
In this thesis, the exploitation of computational fluid dynamics (CFD) methods for the flight dynamics of manoeuvring aircraft is investigated. It is demonstrated that CFD can now be used in a reasonably routine fashion to generate stability and control databases. Different strategies to create CFD-derived simulation models across the flight envelope are explored, ranging from combined low-fidelity/high-fidelity methods to reduced-order modelling. For the representation of the unsteady aerodynamic loads, a model based on aerodynamic derivatives is considered. Static contributions are obtained from steady-state CFD calculations in a routine manner. To more fully account for the aircraft motion, dynamic derivatives are used to update the steady-state predictions with additional contributions. These terms are extracted from small-amplitude oscillatory tests. The numerical simulation of the flow around a moving airframe for the prediction of dynamic derivatives is a computationally expensive task. Results presented are in good agreement with available experimental data for complex geometries. A generic fighter configuration and a transonic cruiser wind tunnel model are the test cases. In the presence of aerodynamic non-linearities, dynamic derivatives exhibit significant dependency on flow and motion parameters, which cannot be reconciled with the model formulation. An approach to evaluate the sensitivity of the non-linear flight simulation model to variations in dynamic derivatives is described. The use of reduced models, based on the manipulation of the full-order model to reduce the cost of calculations, is discussed for the fast prediction of dynamic derivatives. A linearized solution of the unsteady problem, with an attendant loss of generality, is inadequate for studies of flight dynamics because the aircraft may experience large excursions from the reference point. The harmonic balance technique, which approximates the flow solution in a Fourier series sense, retains a more general validity. The model truncation, resolving only a small subset of frequencies typically restricted to include one Fourier mode at the frequency at which dynamic derivatives are desired, provides accurate predictions over a range of two- and three-dimensional test cases. While retaining the high fidelity of the full-order model, the cost of calculations is a fraction of the cost for solving the original unsteady problem. An important consideration is the limitation of the conventional model based on aerodynamic derivatives when applied to conditions of practical interest (transonic speeds and high angles of attack). There is a definite need for models with more realism to be used in flight dynamics. To address this demand, various reduced models based on system-identification methods are investigated for a model case. A non-linear model based on aerodynamic derivatives, a multi-input discrete-time Volterra model, a surrogate-based recurrence-framework model, linear indicial functions and radial basis functions trained with neural networks are evaluated. For the flow conditions considered, predictions based on the conventional model are the least accurate. While requiring similar computational resources, improved predictions are achieved using the alternative models investigated. Furthermore, an approach for the automatic generation of aerodynamic tables using CFD is described. To efficiently reduce the number of high-fidelity (physics-based) analyses required, a kriging-based surrogate model is used. The framework is applied to a variety of test cases, and it is illustrated that the approach proposed can handle changes in aircraft geometry. The aerodynamic tables can also be used in real-time to fly the aircraft through the database. This is representative of the role played by CFD simulations and the potential impact that high-fidelity analyses might have to reduce overall costs and design cycle time.
14
Currie, Martin, and Ingrid Kubin. "Fixed price dynamics versus flexible price dynamics." Inst. für Volkswirtschaftstheorie und -politik, WU Vienna University of Economics and Business, 2005. http://epub.wu.ac.at/114/1/document.pdf.
Abstract:
This paper contrasts the dynamical behaviors of fixed and flexible price regimes for a monopolistically competitive manufacturing sector in which firms base decisions on expectations about product demands. (author's abstract)Series: Department of Economics Working Paper Series
15
Mokhtarian, Farzad. "Fluid dynamics of airfoils with moving surface boundary-layer control." Thesis, University of British Columbia, 1988. http://hdl.handle.net/2429/29026.
Abstract:
The concept of moving surface boundary-layer control, as applied to the Joukowsky and NACA airfoils, is investigated through a planned experimental program complemented by theoretical and flow visualization studies. The moving surface was provided by one or two rotating cylinders located at the leading edge, the trailing edge, or the top surface of the airfoil. Three carefully designed two-dimensional models, which provided a wide range of single and twin cylinder configurations, were tested at a subcritical Reynolds number (Re = 4.62 x 10⁴ or Re — 2.31 x 10⁵) in a laminar-flow tunnel over a range of angles of attack and cylinder rotational speeds. The test results suggest that the concept is indeed quite promising and can provide a substantial increase in lift and a delay in stall.
The leading-edge rotating cylinder effectively extends the lift curve without substantially
affecting its slope. When used in conjunction with a second cylinder on the upper surface, further improvements in the maximum lift and stall angle are possible. The maximum coefficient of lift realized was around 2.22, approximately 2.6 times that of the base airfoil. The maximum delay in stall was to around 45°. In general, the performance improves with an increase in the ratio of cylinder surface speed (Uc) to the free stream speed (U). However, the additional benefit derived progressively diminishes with an increase in Uc/U and becomes virtually negligible for Uc/U > 5.
There appears to be an optimum location for the leading-edge-cylinder. Tests with the cylinder at the upper side of the leading edge gave quite promising results. Although the CLmax obtained was a little lower than the two-cylinder configuration (1.95 against 2.22), it offers a major advantage in terms of mechanical simplicity. Performance of the leading-edge-cylinder also depends on its geometry. A scooped configuration appears to improve performance at lower values of Uc/U (Uc/U ≤ 1). However, at higher rates of rotation the free stream is insensitive to the cylinder geometry and there is no particular advantage in using the scooped geometry.
A rotating trailing-edge-cylinder affects the airfoil characteristics in a fundamentally different manner. In contrast to the leading-edge-cylinder, it acts as a flap by shifting the CL vs. α plots to the left thus increasing the lift coefficient at smaller angles of attack before stall. For example, at α = 4°, it changed the lift coefficient from 0.35 to 1.5, an increase of 330%. Thus in conjunction with the leading-edge- cylinder, it can provide significant improvements in lift over the entire range of small to moderately high angles of incidence (α ≤ 18°).
On the theoretical side, to start with, the simple conformal transformation approach
is used to obtain a closed form potential-flow solution for the leading-edge-cylinder configuration. Though highly approximate, the solution does predict correct trends and can be used at a relatively small angle of attack. This is followed by an extensive numerical study of the problem using:
• the surface singularity approach including wall confinement and separated flow effects;
• a finite-difference boundary-layer scheme to account for viscous corrections; and
• an iteration procedure to construct an equivalent airfoil, in accordance with the local displacement thickness of the boundary layer, and to arrive at an estimate for the pressure distribution.
Effect of the cylinder is considered either through the concept of slip velocity or a pair of counter-rotating vortices located below the leading edge. This significantly
improves the correlation. However, discrepancies between experimental and numerical results do remain. Although the numerical model generally predicts CLmax with a reasonable accuracy, the stall estimate is often off because of an error in the slope of the lift curve. This is partly attributed to the spanwise flow at the model during the wind tunnel tests due to gaps in the tunnel floor and ceiling required for the connections to the externally located model support and cylinder drive motor. However, the main reason is the complex character of the unsteady flow with separation and reattachment, resulting in a bubble, which the present numerical
procedure does not model adequately. It is expected that better modelling of the cylinder rotation with the slip velocity depending on a dissipation function, rotation, and angle of attack should considerably improve the situation.
Finally, a flow visualization study substantiates, rather spectacularly, effectiveness
of the moving surface boundary-layer control and qualitatively confirms complex
character of the flow as predicted by the experimental data.Applied Science, Faculty of
Mechanical Engineering, Department of
Graduate
16
Ozaki, Junichi. "Dynamical quantum effects in cluster dynamics of Fermi systems." 京都大学 (Kyoto University), 2015. http://hdl.handle.net/2433/199083.
17
Wu, Ye. "Nonlinear dynamics in complex networks and modeling human dynamics." Phd thesis, Universität Potsdam, 2010. http://opus.kobv.de/ubp/volltexte/2010/4735/.
Abstract:
Durch große Datenmengen können die Forscher die Eigenschaften komplexer Systeme untersuchen, z.B. komplexe Netzwerk und die Dynamik des menschlichen Verhaltens. Eine große Anzahl an Systemen werden als große und komplexe Netzwerke dargestellt, z.B. das Internet, Stromnetze, Wirtschaftssysteme. Immer mehr Forscher haben großes Interesse an der Dynamik des komplexen Netzwerks.
Diese Arbeit besteht aus den folgenden drei Teilen. Der erste Teil ist ein einfacher dynamischer Optimierungs-Kopplungs-Mechanismus, aber sehr wirksam. Durch den Mechanismus kann synchronisation in komplexen Netzwerken mit und ohne Zeitverzögerung realisiert, und die Fähigkeit der Synchronisation von small-world und scale-free Netze verbessert werden.
Im zweiten Teil geht um die Verstärkung der Robustheit der scale-free Netze im Zusammenhang mit der Gemeinden-Struktur. Einige Reaktionsmuster und topologische Gemeinden sind einheitlich. Die Ergebnisse zeigen einen neuen Aspekt der Beziehung zwischen den Funktionen und der Netzwerk-Topologie von komplexen Netzwerken.
Im dritten Teil welche eine wichtige Rolle in komplexen Netzwerken spielt, wird die Verhaltens-Dynamik der menschliche Mitteilung durch Daten- und Modellanalysierung erforscht, dann entsteht ein neues Mitteilungsmodell. Mit Hilfe von einem Interaktion priority-Queue Model kann das neue Modell erklärt werden. Mit Hilfe des Models können viele praktische Interaktions-Systeme erklärt werden, z.B. E-Mail und Briefe (oder Post). Mit Hilfe meiner Untersuchung kann man menschliches Verhalten auf der Individuums- und Netzwerkebene neu kennenlernen.
Im vierter Teil kann ich nachweisen, dass menschliches Kommentar-Verhalten in on-line Sozialsystemen, eine andere Art der Interaktionsdynamik von Mensch non-Poisson ist und dieses am Modell erklären. Mit Hilfe der non-Poisson Prozesse kann man das persönliche Anziehungskraft-Modell besser verstehen. Die Ergebnisse sind hilfreich zum Kennenlernen des Musters des menschlichen Verhaltens in on-line Gesellschaften und der Entwicklung von öffentlicher Meinung nicht nur in der virtuellen Gesellschaftn sondern auch in der Realgesellschaft.
Am Ende geht es um eine Prognose von menschlicher Dynamik und komplexen Netzwerken.The availability of large data sets has allowed researchers to uncover complex properties in complex systems, such as complex networks and human dynamics. A vast number of systems, from the Internet to the brain, power grids, ecosystems, can be represented as large complex networks. Dynamics on and of complex networks has attracted more and more researchers’ interest. In this thesis, first, I introduced a simple but effective dynamical optimization coupling scheme which can realize complete synchronization in networks with undelayed and delayed couplings and enhance the small-world and scale-free networks’ synchronizability. Second, I showed that the robustness of scale-free networks with community structure was enhanced due to the existence of communities in the networks and some of the response patterns were found to coincide with topological communities. My results provide insights into the relationship between network topology and the functional organization in complex networks from another viewpoint. Third, as an important kind of nodes of complex networks, human detailed correspondence dynamics was studied by both data and the model. A new and general type of human correspondence pattern was found and an interacting priority-queues model was introduced to explain it. The model can also embrace a range of realistic social interacting systems such as email and letter communication. My findings provide insight into various human activities both at the individual and network level. Fourth, I present clearly new evidence that human comment behavior in on-line social systems, a different type of interacting human dynamics, is non-Poissonian and a model based on the personal attraction was introduced to explain it. These results are helpful for discovering regular patterns of human behavior in on-line society and the evolution of the public opinion on the virtual as well as real society. Finally, there are conclusion and outlook of human dynamics and complex networks.
18
Feng, Chih-Liang. "Heavy truck dynamics modeling using multi-body dynamics." The Ohio State University, 1996. http://rave.ohiolink.edu/etdc/view?acc_num=osu1295551522.
19
Yamashita, Hiroki. "Flexible multibody dynamics approach for tire dynamics simulation." Diss., University of Iowa, 2016. https://ir.uiowa.edu/etd/2297.
Abstract:
The objective of this study is to develop a high-fidelity physics-based flexible tire model that can be fully integrated into multibody dynamics computer algorithms for use in on-road and off-road vehicle dynamics simulation without ad-hoc co-simulation techniques. Despite the fact detailed finite element tire models using explicit finite element software have been widely utilized for structural design of tires by tire manufactures, it is recognized in the tire industry that existing state-of-the-art explicit finite element tire models are not capable of predicting the transient tire force characteristics accurately under severe vehicle maneuvering conditions due to the numerical instability that is essentially inevitable for explicit finite element procedures for severe loading scenarios and the lack of transient (dynamic) tire friction model suited for FE tire models. Furthermore, to integrate the deformable tire models into multibody full vehicle simulation, co-simulation technique could be an option for commercial software. However, there exist various challenges in co-simulation for the transient vehicle maneuvering simulation in terms of numerical stability and computational efficiency. The transient tire dynamics involves rapid changes in contact forces due to the abrupt braking and steering input, thus use of co-simulation requires very small step size to ensure the numerical stability and energy balance between two separate simulation using different solvers.
In order to address these essential and challenging issues on the high-fidelity flexible tire model suited for multibody vehicle dynamics simulation, a physics-based tire model using the flexible multibody dynamics approach is proposed in this study. To this end, a continuum mechanics based shear deformable laminated composite shell element is developed based on the finite element absolute nodal coordinate formulation for modeling the complex fiber reinforced rubber tire structure. The assumed natural strain (ANS) and enhanced assumed strain (EAS) approaches are introduced for alleviating element lockings exhibited in the element. Use of the concept of the absolute nodal coordinate formulation leads to various advantages for tire dynamics simulation in that (1) constant mass matrix can be obtained for fully nonlinear dynamics simulation; (2) exact modeling of rigid body motion is ensured when strains are zero; and (3) non-incremental solution procedure utilized in the general multibody dynamics computer algorithm can be directly applied without specialized updating schemes for finite rotations. Using the proposed shear deformable laminated composite shell element, a physics-based flexible tire model is developed. To account for the transient tire friction characteristics including the friction-induced hysteresis that appears in severe maneuvering conditions, the distributed parameter LuGre tire friction model is integrated into the flexible tire model. To this end, the contact patch predicted by the structural tire model is discretized into small strips across the tire width, and then each strip is further discretized into small elements to convert the partial differential equations of the LuGre tire friction model to the set of first-order ordinary differential equations. By doing so, the structural deformation of the flexible tire model and the LuGre tire friction force model are dynamically coupled in the final form of the equations, and these equations are integrated simultaneously forward in time at every time step.
Furthermore, a systematic and automated procedure for parameter identification of LuGre tire friction model is developed. Since several fitting parameters are introduced to account for the nonlinear friction characteristics, the correlation of the model parameters with physical quantities are not clear, making the parameter identification of the LuGre tire friction model difficult. In the procedure developed in this study, friction parameters in terms of slip-dependent friction characteristics and adhesion parameter are estimated separately, and then all the parameters are identified using the nonlinear least squares fitting. Furthermore, the modified friction characteristic curve function is proposed for wet road conditions, in which the linear decay in friction is exhibited in the large slip velocity range. It is shown that use of the proposed numerical procedure leads to an accurate prediction of the LuGre model parameters for measured tire force characteristics under various loading and speed conditions. Furthermore, the fundamental tire properties including the load-deflection curve, the contact patch lengths, contact pressure distributions, and natural frequencies are validated against the test data. Several numerical examples for hard braking and cornering simulation are presented to demonstrate capabilities of the physics-based flexible tire model developed in this study.
Finally, the physics-based flexible tire model is further extended for application to off-road mobility simulation. To this end, a locking-free 9-node brick element with the curvature coordinates at the center node is developed and justified for use in modeling a continuum soil with the capped Drucker-Prager failure criterion. Multiplicative finite strain plasticity theory is utilized to consider the large soil deformation exhibited in the tire/soil interaction simulation. In order to identify soil parameters including cohesion and friction angle, the triaxial soil test is conducted. Using the soil parameters identified including the plastic hardening parameters by the compression soil test, the continuum soil model developed is validated against the test data. Use of the high-fidelity physics-based tire/soil simulation model in off-road mobility simulation, however, leads to a very large computational model to consider a wide area of terrains. Thus, the computational cost dramatically increases as the size of the soil model increases. To address this issue, the component soil model is proposed such that soil elements far behind the tire can be removed from the equations of motion sequentially, and then new soil elements are added to the portion that the tire is heading to. That is, the soil behavior only in the vicinity of the rolling tire is solved in order to reduce the overall model dimensionality associated with the finite element soil model. It is shown that use of the component soil model leads to a significant reduction in computational time while ensuring the accuracy, making the use of the physics-based deformable tire/soil simulation capability feasible in off-road mobility simulation.
20
Ebadi, Haleh. "Boolean functions and discrete dynamics: analytic and biological application." Doctoral thesis, Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-205944.
Abstract:
Modeling complex gene interacting systems as Boolean networks lead to
a significant simplification of computational investigation. This can be
achieved by discretization of the expression level to ON or OFF states and
classifying the interactions to inhibitory and activating. In this respect,
Boolean functions are responsible for the evolution of the binary elements of
the Boolean networks. In this thesis, we investigate the mostly used Boolean
functions in modeling gene regulatory networks. Moreover, we introduce
a new type of function with strong inhibitory namely the veto function.
Our computational and analytic studies on the verity of the networks capable
of constructing the same State Transition Graph lead to define a new
concept namely the “degeneracy” of Boolean functions. We further derive
analytically the sensitivity of the Boolean functions to perturbations. It
turns out that the veto function forms the most robust dynamics. Furthermore,
we verify the applicability of veto function to model the yeast cell
cycle networks. In particular, we show that in an intracellular signal transduction
network [Helikar et al, PNAS (2008)], the functions with veto are
over-represented by a factor exceeding the over-representation of threshold
functions and canalyzing functions in the same system. The statistics of
the connections of the functional networks are studied in detail. Finally,
we look at a different scale of biological phenomena using a binary model.
We propose a simple correlation-based model to describe the pattern formation
of Fly eye. Specifically, we model two different procedures of Fly eye
formation, and provide a generic approach for Fly eye simulation.
21
Castro, Arnoldo. "Modeling and dynamic analysis of a two-wheeled inverted-pendulum." Thesis, Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/44897.
Abstract:
There is a need for smaller and more economic transportation systems. Two-wheeled inverted-pendulum machines, such as the Segway, have been proposed to address this need. However, the Segway places the operator on top of a naturally unstable platform that is stabilized by means of a control system. The control stability of the Segway can be severely affected when minor disturbances or unanticipated conditions arise. In this thesis, a dynamic model of a Segway is developed and used in simulations of various conditions that can arise during normal use. The dynamic model of a general two-wheeled inverted pendulum and human rider is presented. Initial estimates of the parameters were calculated or obtained from other references. The results from numerous experiments are presented and used to develop a better understanding of the dynamics of the vehicle. The experimental data was then used to adjust the model parameters to match the dynamics of a real Segway Human Transporter. Finally, the model was used to simulate various failure conditions. The simulations provide a better understanding of how these conditions arise, and help identify which parameters play an important role in their outcome.
22
Chambers, Steven B. "Investigation of combustive flows and dynamic meshing in computational fluid dynamics." Thesis, Texas A&M University, 2004. http://hdl.handle.net/1969.1/1324.
Abstract:
Computational Fluid Dynamics (CFD) is a field that is constantly advancing. Its advances in terms of capabilities are a result of new theories, faster computers, and new numerical methods. In this thesis, advances in the computational fluid dynamic modeling of moving bodies and combustive flows are investigated. Thus, the basic theory behind CFD is being extended to solve a new class of problems that are generally more complex. The first chapter that investigates some of the results, chapter IV, discusses a technique developed to model unsteady aerodynamics with moving boundaries such as flapping winged flight. This will include mesh deformation and fluid dynamics theory needed to solve such a complex system. Chapter V will examine the numerical modeling of a combustive flow. A three dimensional single vane burner combustion chamber is numerically modeled. Species balance equations along with rates of reactions are introduced when modeling combustive flows and these expressions are discussed. A reaction mechanism is validated for use with in situ reheat simulations. Chapter VI compares numerical results with a laminar methane flame experiment to further investigate the capabilities of CFD to simulate a combustive flow. A new method of examining a combustive flow is introduced by looking at the solutions ability to satisfy the second law of thermodynamics. All laminar flame simulations are found to be in violation of the entropy inequality.
23
Kachani, Soulaymane, and Georgia Perakis. "Modeling Travel Times in Dynamic Transportation Networks; A Fluid Dynamics Approach." Massachusetts Institute of Technology, Operations Research Center, 2001. http://hdl.handle.net/1721.1/5224.
Abstract:
In this paper, we take a fluid dynamics approach to determine the travel time in traversing a network's link. We propose a general model for travel time functions that utilizes fluid dynamics laws for compressible flow to capture a variety of flow patterns such as the formation and dissipation of queues, drivers' response to upstream congestion or decongestion and drivers' reaction time. We examine two variants of the model, in the case of separable velocity functions, which gives rise to two families of travel time functions for the problem; a polynomial and an exponential family. We analyze these travel time functions and examine several special cases. Our investigation also extends to the case of non-separable velocity functions starting with an analysis of the interaction between two links, and then extending it to the general case of acyclic networks.
24
Gaddoni, Giacomo. "Modeling of Evolutionary Cancer Dynamics and Optimal Treatment via Dynamic Programming." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021.
Abstract:
Cancer is one of the biggest challenges in healthcare. Fast diagnosis and personalized pharmacological therapies are essential for lowering the mortality rate. In this thesis, we propose a general-purpose model for cancer and an optimal control strategy to minimize its volume. Firstly, we analyze the literature about cancer in the System and Control community and produce a taxonomy of cancer typologies. We identify four main behaviors arising in these models: growth, mutation, migration, and drug response. After this preliminary analysis, we propose a cancer treatment model based on Ordinary Differential Equations (ODEs) and Evolutionary Game Theory, that captures these dynamics more generally. ODEs provide a framework for lumped-parameters representations, and Evolutionary Game Theory provides tools to describe competitive behaviors typical of these cell populations. Starting from this taxonomy, we chose a model representable with a 2-node graph that expressed all the dynamics of cancer processes. We studied the model, discretized it, and applied an optimal control method based on Differential Dynamic Programming (DDP). Bounded and unbounded DDP were ineffective. It was necessary to introduce regularized DDP via adaptive shift. With this algorithm, the results are promising: the system is successfully stabilized in the origin. It is also possible to control the system, driving it between two equilibria, tracking a demanded trajectory. Most of the testing was done in MATLAB. Then, the project was ported to Python. This was done to facilitate future expansion of the model and control strategies through scientific analysis toolboxes and frameworks.
25
Lee, SeeWoo. "Development of new dynamic tire model for improved vehicle dynamics simulation." The Ohio State University, 1994. http://rave.ohiolink.edu/etdc/view?acc_num=osu1334584006.
26
Abbs, Brandon Robert. "The temporal dynamics of auditory memory for static and dynamic sounds." Diss., University of Iowa, 2008. http://ir.uiowa.edu/etd/4.
27
Rupp, Matthew Y. "Passive dynamic steering system model for use in vehicle dynamics simulation." Connect to resource, 1994. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1157568618.
28
Striebel, Maren. "PLANKTON DYNAMICS." Diss., lmu, 2008. http://nbn-resolving.de/urn:nbn:de:bvb:19-92597.
29
Richardson, Derek C. "Planetesimal dynamics." Thesis, University of Cambridge, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.309052.
30
Hunton, B. J. "Vortex dynamics." Thesis, University of Oxford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.259909.
31
Stadin, Karolina. "Employment Dynamics." Doctoral thesis, Uppsala universitet, Nationalekonomiska institutionen, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-221561.
Abstract:
The main focus of this thesis is the employment decisions of firms. The thesis consists of three self-contained but closely related essays, all enlightening employment dynamics in different ways. The thesis is mainly empirical but there are also some theoretical developments when existing theory is insufficient to explain the empirical findings. The impact on employment of product market conditions and labor market conditions facing firms are investigated. The results suggest that product demand has a robust impact on firms’ employment dynamics, but also the market price, the wage costs, and the matching between vacancies and unemployed workers seem to matter. The empirical evidence of the relevance of imperfect competition in the product market is important, particularly since most research on labor market dynamics has assumed perfect competition. The results with respect to matching of vacancies and unemployed workers contradict the standard search and matching model as well as simple efficiency-wage or bargaining models with wage rigidity and excess supply but no frictions in the labor market. A richer model of the labor market is needed to explain the results, including on-the-job search and perhaps more heterogeneity between employed and unemployed workers. Essay I, “What are the Determinants of Hiring? - The Role of Demand and Supply Factors”, studies the importance of demand and supply factors for hiring in local labor markets. Essay II, “Vacancy Matching and Labor Market Conditions”, studies the probability of filling a vacancy, how it varies with the number of unemployed and the number of vacancies in the local labor market, and what impact it has on firms’ employment dynamics. Essay III, “The Dynamics of Firms’ Factor Demand”, studies firm-level adjustments of employment, the capital stock, and inventories in response to exogenous shocks theoretically and empirically. These three decisions have typically been studied one at the time, but here they are studied together in a way which allows for interactions and a better understanding of firm behavior.
32
Still, G. Keith. "Crowd dynamics." Thesis, University of Warwick, 2000. http://wrap.warwick.ac.uk/36364/.
Abstract:
Crowd dynamics are complex. This thesis examines the nature of the crowd and its dynamics with specific reference to the issues of crowd safety. A model (Legion) was developed that simulates the crowd as an emergent phenomenon using simulated annealing and mobile cellular automata. We outline the elements of that model based on the interaction of four parameters: Objective, Motility, Constraint and Assimilation. The model treats every entity as an individual and it can simulate how people read and react to their environment in a variety of conditions. Which allows the user to study a wide range of crowd dynamics in different geometries and highlights the interactions of the crowd with their environment. We demonstrate that the model runs in polynomial time and can be used to assess the limits of crowd safety during normal and emergency egress. Over the last 10 years there have been many incidents of crowd related disasters. We highlight deficiencies in the existing guidelines relating to crowds. We compare and contrast the model with the safety guidelines and highlight specific areas where the guides may be improved. We demonstrate that the model is capable of reproducing these dynamics without additional parameters, satisfying Occam's Razor. The model is tested against known crowd dynamics from field studies, including Wembley Stadium, Balham Station and the Hong Kong Jockey club. We propose an alternative approach to assessing the dynamics of the crowd through the use of the simulation and analysis of least effort behaviour. Finally we test the model in a variety of applications where crowd related incidents warrant structural alterations at client sites. We demonstrate that the model explains the variance in a variety of field measurements, that it is robust and that it can be applied to future designs where safety and crowd comfort are criteria for design and cost savings.
33
Dean, David Stanley. "Stochastic dynamics." Thesis, University of Cambridge, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318048.
34
Boksha, Victor Vladimir 1960. "Microlithography dynamics." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/9288.
Abstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Sloan School of Management, 2000.Includes bibliographical references (leaves 128-129).
This work focuses on historical and modern geography-related analysis of semiconductor industry (specifically microlithography) and its role in Information Technology (IT). Following Professor's J.D.Sachs terminology, it would be highly desirable "to distinguish the growth effects of the various [in my case, related to IT, VB] components of economic policy". Structurally, thesis offers an analysis of the latest business cases (partially from the author's experiences with semiconductor equipment makers, Integrated Circuits (IC) makers, and "agglomeration economies" such as in Europe, Asia and Silicon Valley). I explore the connection of the current microlithography status and its perspectives with the patterns of economy's macrobehavior. I scrutinize hypothesis that, with silicon technology becoming a commodity, the slowdown in introducing new generations of products, based on new integrated circuits' functionality, is critical for semiconductor's industry consistent growth. In its current stage (with microlithography stagnation) the solid-state based IC technology provides only marginal functionality improvements between so called "new" generations and has somewhat limited potential to do so in a future. In summary, the transition processes of growth in the industry reaching the status of being mature are not very encouraging and definitely raise the question: "What happens if the IC industry will start to fail supporting the GDP growth rate established and sustained by the Information Technology ?" I hope that proposed analysis will help to understand better the unjustifiable expectations from the technology, which may lead to distorted policies of capital investment if coupled with illusions of unlimited economy expansion. The economic Long Wave Game was redesigned and developed for PC version to create a platform for possible future research in this area. Looking broader I suggest that the ultra-densification of space implemented in the technology of microlithography is the underlying material reason for the IT & space-infened time transformation and consequent social arrhythmia. Finally, I consider it as important that new kind of teams with defining notion of partnership and shared best practices are operationally decisive for an effective organization in the IT environment.
Victor Vladimir Boksha.
S.M.
35
Nicolay, David. "Volatility dynamics." Palaiseau, Ecole polytechnique, 2011. http://pastel.archives-ouvertes.fr/docs/00/60/01/06/PDF/VolatilityDynamics_DNicolay_PrePrint.pdf.
Abstract:
We establish asymptotic links between two classes of stochastic volatility models describing the same derivative market : - a generic stochastic instantaneous volatility (SInsV) model, whose SDE system is a formal Wiener chaos without any specified state variable. - a sliding stochastic implied volatility (SImpV) class, another market model describing explicitly the joint dynamics of the underlying and of the associated European option surface. Each of these connections is achieved by layer, between a group of SInsV coefficients and set of (static and dynamic) SImpV differentials. The asymptotic approach leads to these cross-differentials being taken at the zero-expiry, At-The-Money point. We progress from a simple single-underlying and bi-dimensional setup, first to a multi-dimensional configuration, and then to a term-structure framework. We expose the structural modelling constraints and the asymmetry between the direct problem (from SInsV to SImpV) and the inverse one. We show that this Asymptotic Chaos Expansion (ACE) methodology is a powerful tool for model design and analysis. Focusing on local volatility models and their extensions, we compare ACE with the literature and exhibit a systematic bias in Gatheral's heuristics. In the multi-dimensional context we focus on stochastic-weights baskets, for which ACE provides intuitive results underlining the embedded induction. In the interest rates environment, we derive the first layer of smile descriptors for caplets, swaptions and bond options, within both a SV-HJM and a SV-LMM framework. Also, we prove that ACE can be automated for generic models, at any order, without formal calculus. The interest this algorithm is demonstrated by computing manually the 2nd and 3rd layers, in a generic bi-dimensional SInsV model. We present the applicative potential of ACE for calibration, pricing, hedging or relative value purposes, illustrated with numerical tests on the CEV-SABR modelNous établissons les liens asymptotique entre deux catégories de modèles à volatilité stochastique décrivant le même marché dérivé: - un modèle générique à volatilité stochastique instantanée (SInsV) , dont le système d'EDS est un chaos de Wiener formel, spécifié sans aucune variable d'état. - une classe à volatilité implicite stochastique glissante (SImpV), qui est un autre modèle de marché, décrivant explicitement la dynamique conjointe du sous-jacent et de la surface d'options Européennes associées. Chacune de ces connexions est atteinte couche par couche, entre un groupe de coefficients SInsV et un ensemble de differentielles SImpV (statiques et dynamiques). L'approche asymptotique conduit à ce que ces différentielles croisees soient prises à l'expiration zéro, au point ATM. Nous progressons d'une configuration simple, bi-dimensionnelle à sous-jacent unique, d'abord vers une configuration multi-dimensionnelle, puis vers un cadre à structure par terme. Nous exposons les contraintes structurelles de modélisation et l'asymétrie entre le problème direct (de SInsV vers SImpV) et inverse. Nous montrons que cette expansion asymptotique en chaos (ACE) est un outil puissant pour la conception et l'analyse de modèles. En se concentrant sur des modèles à volatilité locale et leurs extensions, nous comparons ACE avec la littérature et exhibons un biais systématique dans l'heuristique de Gatheral. Dans le contexte multi-dimensionnel, nous nous concentrons sur des paniers à poids stochastiques, pour lesquels ACE fournit des résultats intuitifs soulignant la recurrence naturelle. Dans l'environnement des taux d'intérêt, nous etablissons la première couche de descripteurs du smile pour les caplets, les swaptions et les options sur obligations, à la fois dans un cadre SV-HJM et un cadre SV-LMM. En outre, nous montrons que ACE peut être automatisé pour des modèles génériques, à n'importe quel ordre, sans calcul formel. L'intérêt de cet algorithme est démontré par le calcul manuel des 2eme et 3eme couches, dans un modèle générique SInsV bi-dimensionnel. Nous présentons le potentiel applicatif d'ACE pour la calibration, l'evaluation, la couverture ou à des fins d'arbitrage, illustré par des tests numériques sur le modèle CEV-SABR
36
Dolzhenko, Egor. "Transducer dynamics." [Tampa, Fla] : University of South Florida, 2008. http://purl.fcla.edu/usf/dc/et/SFE0002380.
37
Lambrou, Lambros. "Combinatorial dynamics." Thesis, University of Warwick, 1998. http://wrap.warwick.ac.uk/111075/.
Abstract:
In Chapter 1, we consider many topics that are both combinatorial and dynamical in nature. In particular, we study substitution maps, subword complexity, symbolic dynamics and interval-exchange maps. After describing the basic concepts and notation, we study the subword complexity functions that arise from substitutions connected with /3-transformations. We then make some general observations regarding subword complexity functions associated with substitutions, before going on to study some specific examples with quadratic growth in section 1.4. In section 1.5, we study the symbolic dynamics associated with these types of substitutions, generalising the notions of recurrence, minimality etc. In section 1.6, we briefly describe and compute an invariant measure for the substitutions considered in section 1.4. We then prove a result that describes a connection between the symbolic dynamics and interval-exchange maps, and apply it to these substitution maps. In Chapter 2, we study a dynamical skew-product and some of the combinatorial questions that it raises. In sections 2.1 and 2.2 we describe the skew-product, and explain the connection between it and some one-player games. We then describe and analyse a code-word problem, and explain how we can generalise our results. In sections 2.6 and 2.7, we study a continuous version of the problem and prove a result that might shed some light on the original skew-product. At the end of both chapters, we present some problems which we believe to be still open, and suggest ideas for further research into the topics presented in this thesis.
38
Dolzhenko, Egor. "Transducer dynamics." Scholar Commons, 2007. https://scholarcommons.usf.edu/etd/217.
Abstract:
Transducers are finite state automata with an output. In this thesis, we attempt to classify sequences that can be constructed by iteratively applying a transducer to a given word. We begin exploring this problem by considering sequences of words that can be produced by iterative application of a transducer to a given input word, i.e., identifying sequences of words of the form w, t(w), t²(w), . . . We call such sequences transducer recognizable. Also we introduce the notion of "recognition of a sequence in context", which captures the possibility of concatenating prefix and suffix words to each word in the sequence, so a given sequence of words becomes transducer recognizable. It turns out that all finite and periodic sequences of words of equal length are transducer recognizable. We also show how to construct a deterministic transducer with the least number of states recognizing a given sequence. To each transducer t we associate a two-dimensional language L²(t) consisting of blocks of symbols in the following way. The first row, w, of each block is in the input language of t, the second row is a word that t outputs on input w. Inductively, every subsequent row is a word outputted by the transducer when its preceding row is read as an input. We show a relationship of the entropy values of these two-dimensional languages to the entropy values of the one-dimensional languages that appear as input languages for finite state transducers.
39
Leyendecker, Sigrid. "Mechanical integrators for constrained dynamical systems in flexible multibody dynamics." [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=980411912.
40
Sardanyés, i. Cayuela Josep. "Dynamics, evolution and information in nonlinear dynamical systems of replicators." Doctoral thesis, Universitat Pompeu Fabra, 2009. http://hdl.handle.net/10803/7182.
Abstract:
En aquesta tesi he investigat diversos camps de la biologia que podrien englobar-se en la disciplina general dels sistemes no lineals de replicadors. Els treballs presentats en aquesta tesis investiguen diversos fenomens dinàmics i processos evolutius per virus de RNA, pels anomenats hipercicles i per models generals de replicadors antagonistes. Específicament he investigat les anomenades quasiespècies, utilitzades per a modelitzar poblacions de RNA. Els treballs sobre hipercicles exploren diversos fenomens previs a l'origen de la vida i a l'aparició de la primera cèl.lula vivent. Mitjançant models ecològics com també utilitzant diferents eines computacionals he estudiat l'anomenada hipòtesi de la Reina Roja per entitats replicadores simples amb mutació. Aquests estudis tenen un interès en el contexte de l'evolució prebiòtica i l'ecologia teòrica.In this thesis I have investigated several fields of biology that can be classified in the general subject of replicator nonlinear systems. The works presented in the thesis investigate several dynamical phenomena and evolutionary processes for RNA viruses, for hypercycles and for general models on antagonistic replicator dynamics. I have specifically investigated the dynamics of so-called quasispecies, used for the modelization of RNA populations. The works on hypercycles explore several phenomena related to previous events to the origin of life and to the appearance of the first living cell. By means of some ecologically-based mathematical models as well as of some computational models we also investigate the so-called Red Queen hypothesis for small, replicating-mutating entities. These studies are of interest in the context of prebiotic evolution and theoretical ecology.
41
Mizuno, Hideyuki. "Molecular Dynamics Simulation Studies of Dynamical Properties of Supercooled Liquids." 京都大学 (Kyoto University), 2012. http://hdl.handle.net/2433/157540.
42
Sardanyés, Cayuela Josep. "Dynamics, evolution and information in nonlinear dynamical systems of replicators." Doctoral thesis, Universitat Pompeu Fabra, 2009. http://hdl.handle.net/10803/7182.
Abstract:
En aquesta tesi he investigat diversos camps de la biologia que podrien englobar-se en la disciplina general dels sistemes no lineals de replicadors. Els treballs presentats en aquesta tesis investiguen diversos fenomens dinàmics i processos evolutius per virus de RNA, pels anomenats hipercicles i per models generals de replicadors antagonistes. Específicament he investigat les anomenades quasiespècies, utilitzades per a modelitzar poblacions de RNA. Els treballs sobre hipercicles exploren diversos fenomens previs a l'origen de la vida i a l'aparició de la primera cèl.lula vivent. Mitjançant models ecològics com també utilitzant diferents eines computacionals he estudiat l'anomenada hipòtesi de la Reina Roja per entitats replicadores simples amb mutació. Aquests estudis tenen un interès en el contexte de l'evolució prebiòtica i l'ecologia teòrica.In this thesis I have investigated several fields of biology that can be classified in the general subject of replicator nonlinear systems. The works presented in the thesis investigate several dynamical phenomena and evolutionary processes for RNA viruses, for hypercycles and for general models on antagonistic replicator dynamics. I have specifically investigated the dynamics of so-called quasispecies, used for the modelization of RNA populations. The works on hypercycles explore several phenomena related to previous events to the origin of life and to the appearance of the first living cell. By means of some ecologically-based mathematical models as well as of some computational models we also investigate the so-called Red Queen hypothesis for small, replicating-mutating entities. These studies are of interest in the context of prebiotic evolution and theoretical ecology.
43
SANSONE, ALESSANDRO. "Applications of Nonlinear Dynamics and Complex Systems Theory to Finance." Doctoral thesis, La Sapienza, 2007. http://hdl.handle.net/11573/917404.
44
Currier, Patrick Norman. "A Method for Modeling and Prediction of Ground Vehicle Dynamics and Stability in Autonomous Systems." Diss., Virginia Tech, 2011. http://hdl.handle.net/10919/27632.
Abstract:
A future limitation of autonomous ground vehicle technology is the inability of current algorithmic techniques to successfully predict the allowable dynamic operating ranges of unmanned ground vehicles. A further difficulty presented by real vehicles is that the payloads may and probably will change with unpredictably time as will the terrain on which it is expected to operate. To address this limitation, a methodology has been developed to generate real-time estimations of a vehicleâ s instantaneous Maneuvering Manifold. This approach uses force-moment method techniques to create an adaptive, parameterized vehicle model. A technique is developed for estimation of vehicle load state using internal sensors combined with low-magnitude maneuvers. An unscented Kalman filter based estimator is then used to estimate tire forces for use in determining the ground/tire coefficient of friction. Probabilistic techniques are then combined with a combined-slip pneumatic trail based estimator to estimate the coefficient of friction in real-time. This data is then combined to map out the instantaneous maneuvering manifold while applying techniques to account for dynamic rollover and stability limitations. The algorithms are implemented in MATLAB, simulated against TruckSim models, and results are shown to demonstrate the validity of the techniques. The developed methodology is shown to be a novel approach that is capable of addressing the problem of successfully estimating the available maneuvering manifold for autonomous ground vehicles.Ph. D.
45
Hughes, Jonathan L. "Applications of Stability Analysis to Nonlinear Discrete Dynamical Systems Modeling Interactions." VCU Scholars Compass, 2015. http://scholarscompass.vcu.edu/etd/3819.
Abstract:
Many of the phenomena studied in the natural and social sciences are governed by processes which are discrete and nonlinear in nature, while the most highly developed and commonly used mathematical models are linear and continuous. There are significant differences between the discrete and the continuous, the nonlinear and the linear cases, and the development of mathematical models which exhibit the discrete, nonlinear properties occurring in nature and society is critical to future scientific progress. This thesis presents the basic theory of discrete dynamical systems and stability analysis and explores several applications of this theory to nonlinear systems which model interactions involving economic agents and biological populations. In particular we will explore the stability properties of equilibria associated with inter-species and intergenerational population dynamics in biology and market price and agent composition dynamics in economics.
46
Safarzynska, Karolina, and den Bergh Jeroen van. "Beyond Replicator Dynamics: Innovation-Selection Dynamics and Optimal Diversity." Elsevier Science, 2011. http://dx.doi.org/10.1016/j.jebo.2011.01.008.
Abstract:
We propose a new evolutionary approach to model technological change based on an
extension of replicator dynamics with recombination and mutation. It gives rise to interactive
innovation-selection dynamics. The model allows studying the combined effects of selection
and variety generation on evolutionary-economic change. The developed framework
describes a population of boundedly rational entrepreneurs who decide each period on the
allocation of investments in different production technologies. They tend to invest in belowaverage
cost technologies, just as under replicator dynamics. In addition, they spend a
constant fraction of investments, captured by mutation and recombination rates, on alternative
technologies and research on recombinant innovation. As opposed to most previous studies,
mutation and recombination are here conceptual variables with a concrete behavioral
interpretation, namely describing the decision rules (heuristics) of investors. We compare the
dynamics of shares of investments in various technologies for three cases: with constant costs
of capital, with costs decreasing steadily and exogenously over time, and with costs
depending on the level of cumulative investments. For each model version, we examine under
which conditions the coexistence of technological options is feasible and optimal in terms of
minimising the average cost of investments.(authors' abstract)
47
Pagliuca, Giampaolo. "Model reduction for flight dynamics using computational fluid dynamics." Thesis, University of Liverpool, 2018. http://livrepository.liverpool.ac.uk/3029018/.
Abstract:
The coupling of computational fluid dynamics and rigid body dynamics promises enhanced multidisciplinary simulation capability for aircraft design and certification. Industrial application of such coupled simulations is limited however by computational cost. In this context, model reduction can retain the fidelity of the underlying model while decreasing the overall computational effort. Thus, investigation of such coupled model reduction is presented in this thesis. The technique described herein relies on an expansion of the full order non-linear residual function in a truncated Taylor series and subsequent projection onto a small modal basis. Two procedures are outlined to obtain modes for the projection. First, flight dynamics eigenmodes are obtained with an operator-based identification procedure which is capable of calculating the global modes of the coupled Jacobian matrix related to flight dynamics without computing all the modes of the system. Secondly, proper orthogonal decomposition is used as a data-based method to obtain modes representing the coupled system subject to external disturbances such as gusts. Benefits and limitations of the two methods are investigated by analysing results for both initial and external disturbance simulations. Three test cases of increasing complexity are presented. First, an aerofoil, free to translate vertically and rotate, is investigated with aerodynamics based on the Euler equations. Secondly, a two-dimensional wing-tail configuration is studied for longitudinal dynamics. Aerodynamics is modelled with Reynolds-averaged Navier-Stokes equations and Spalart-Allmaras turbulence model. Thirdly, a three-dimensional industrial use case, which concerns a large civil aircraft, is investigated and longitudinal as well as lateral dynamics are both taken into account. Overall, reduced order models relying on both operator-based and data-based identifications are able to retain the accuracy of the high-fidelity tools to predict accurately flight dynamics responses and loads while reducing the computational cost by up to two orders of magnitude. If adopted, these techniques are expected to speed-up aircraft design and lowering certification costs with the final aim of reduced expense for airlines and, as a consequence, for flying passengers.
48
Goldsztein, Guillermo H. (Guillermo Hugo 1969. "On bubble dynamics and gas dynamics in open tubes." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/42773.
49
Mertig, Normann. "Complex Paths for Regular-to-Chaotic Tunneling Rates." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-125920.
Abstract:
Tunneling is a fundamental effect of quantum mechanics, which allows waves to penetrate into regions that are inaccessible by classical dynamics. We study this phenomenon for generic non-integrable systems with a mixed phase space, where tunneling occurs between the classically separated phase-space regions of regular and chaotic motion. We derive a semiclassical prediction for the corresponding tunneling rates from the regular region to the chaotic sea. This prediction is based on paths which connect the regular and the chaotic region in complexified phase space. We show that these complex paths can be constructed despite the obstacle of natural boundaries. For the standard map we demonstrate that tunneling rates can be predicted with high accuracy, by using only a few dominant complex paths. This gives the semiclassical foundation for the long-conjectured and often-observed exponential scaling with Planck's constant of regular-to-chaotic tunneling rates.
50
Epiphaniou, Nicholas. "Modelling of Dynamic Friction Across Solid Material Interfaces Using Molecular Dynamics Techniques." Thesis, Cranfield University, 2009. http://hdl.handle.net/1826/4458.
Abstract:
The topic of this PhD is to investigate materials interfaces under the application of com-pressive forces and dynamic friction. Friction studies are important in applications for high-speed machining and ballistic penetration modelling, two areas where it is important to understand the behaviour of rapidly moving interfaces. Gaining insight into the velocity dependence of the effective tangential force, and its time-evolution, under various external loads is also of particular interest. It is important to understand on an atomic and/or molec-ular level the fundamentals of tribological processes. Some of the processes investigated in this thesis include plastic deformation due to high compression, the response of materials when sliding occurs in terms of temperature variation across the interface and its relation-ship with atomic diffusion. Moreover, the materials dependence on operating conditions of temperature, loading and dynamic friction are factors that ultimately determine the design of tribological systems.
In the last few years it has been shown that materials properties depend on the size, as smaller specimens are relatively stronger than larger ones. This thesis is aiming to em-ploy state of the art numerical and theoretical methods, which are vital to give a significant insight and understanding of the fundamental issues concerning dynamic friction of tribo-logical processes at the atomic scale. The mechanical behaviour is investigated in detail to reveal an accurate theoretical description of the frictional force at metallic surfaces. Special consideration is taken into account for the mechanism that causes dissipation in the form of heat. The strong deformation when materials undergo dynamic friction causes energy to dissipate away from the interface at a high rate.
Additionally, investigation of the plastic deformation and its variation under conditions prevalent at high speed sliding is carried out. Knowledge of the yield point under these conditions is important to obtain accurate constitutive models for the shear stresses. In-vestigating how the material strength varies under sliding friction and obtaining accurate evaluation of the stresses involved has proved difficult and time consuming. This is primar¬ily attributed to the fact that experiments are difficult to conduct and expensive facilities are required. This thesis focuses on aspects of this complex process with the aid of molecular dynamic simulations.