Can dynamical systems approach turbulence?
NASA Astrophysics Data System (ADS)
Holmes, Philip
I review some ideas and methods from dynamical systems theory and discuss applications, actual and potential, to the study of fully developed turbulent flows in an open system: the wall region of a boundary layer. After a brief account of applications to a closed flow system, the approach I concentrate on attempts a marriage between statistical methods and deterministic dynamical systems, both orderly and chaotic. Specifically, coherent structures are identified with combinations of certain basis functions using the proper orthogonal decomposition. A relatively low dimensional ordinary differential equation describing the dynamical interactions of a set of these spatially organized structures is then derived by Galerkin projection of the Navier-Stokes equations. The resulting system is optimal in the sense that it retains the greatest turbulent kinetic energy, in a time averaged sense, among all projections of the same dimension. The model is analyzed using the methods of dynamical systems and symmetries are found to play a crucial rôle. In particular, structurally and asymptotically stable heteroclinic cycles emerge as a common feature in models of various dimensions and orbits attracted to these cycles lead to solutions exhibiting intermittent, violent "events," which appear to reproduce key features of the bursting process. I speculate on the validity of this approach, the "understanding" of turbulent processes it offers and on how some of the gaps in the procedure might be bridged. I do not suggest that this is the only way in which dynamical systems methods can be used, but it is one which seems worth pursuing.
Compressive Information Extraction: A Dynamical Systems Approach
2016-01-24
AFRL-AFOSR-VA-TR-2016-0097 Compressive Information Extraction A Dynamical Systems Approach Mario Sznaier NORTHEASTERN UNIVERSITY Final Report 02/09...Final Performance 3. DATES COVERED (From - To) 01-06-2012 to 31-05-2015 4. TITLE AND SUBTITLE Compressive Information Extraction A Dynamical Systems ... information extraction, hybrid system identification 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT UU 18. NUMBER OF PAGES 19a. NAME OF
Dynamical Systems Approaches to Emotional Development
ERIC Educational Resources Information Center
Camras, Linda A.; Witherington, David C.
2005-01-01
Within the last 20 years, transitions in the conceptualization of emotion and its development have given rise to calls for an explanatory framework that captures emotional development in all its organizational complexity and variability. Recent attempts have been made to couch emotional development in terms of a dynamical systems approach through…
Smart dynamic system design: an integrated approach
NASA Astrophysics Data System (ADS)
Carpenter, Mike J.; Skelton, Robert T.
1994-05-01
A dynamic system with satisfactory performance generally consists of a mechanical system (the plant) and a controller that drives the mechanical system to meet certain performance requirements. Traditionally the control engineer designs the controller only after the plant design is completed. This two-step approach to plant and controller design does not provide the best system design because the dynamics of the plant and the dynamics of the controller often oppose each other. This paper presents an application of the iterative system equivalent optimal mix algorithm to perform a smart design of a nine-member truss substructure and its accompanying controller. The objective of the design algorithm is to reduce the amount of energy used by the controller to maintain control performance, subject to the structure design constraints. Two unique features of the algorithm are that each iteration of the design problem is stated as a convex quadratic programming problem, and the control effort monotonically converges to its final value.
Stability threshold approach for complex dynamical systems
NASA Astrophysics Data System (ADS)
Klinshov, Vladimir V.; Nekorkin, Vladimir I.; Kurths, Jürgen
2016-01-01
A new measure to characterize the stability of complex dynamical systems against large perturbations is suggested, the stability threshold (ST). It quantifies the magnitude of the weakest perturbation capable of disrupting the system and switch it to an undesired dynamical regime. In the phase space, the ST corresponds to the ‘thinnest site’ of the attraction basin and therefore indicates the most ‘dangerous’ direction of perturbations. We introduce a computational algorithm for quantification of the ST and demonstrate that the suggested approach is effective and provides important insights. The generality of the obtained results defines their vast potential for application in such fields as engineering, neuroscience, power grids, Earth science and many others where the robustness of complex systems is studied.
Dynamical Systems in Psychology: Linguistic Approaches
NASA Astrophysics Data System (ADS)
Sulis, William
Major goals for psychoanalysis and psychology are the description, analysis, prediction, and control of behaviour. Natural language has long provided the medium for the formulation of our theoretical understanding of behavior. But with the advent of nonlinear dynamics, a new language has appeared which offers promise to provide a quantitative theory of behaviour. In this paper, some of the limitations of natural and formal languages are discussed. Several approaches to understanding the links between natural and formal languages, as applied to the study of behavior, are discussed. These include symbolic dynamics, Moore's generalized shifts, Crutchfield's ɛ machines, and dynamical automata.
Dynamical Systems Approach to Endothelial Heterogeneity
Regan, Erzsébet Ravasz; Aird, William C.
2012-01-01
Rationale Objective Here we reexamine our current understanding of the molecular basis of endothelial heterogeneity. We introduce multistability as a new explanatory framework in vascular biology. Methods We draw on the field of non-linear dynamics to propose a dynamical systems framework for modeling multistability and its derivative properties, including robustness, memory, and plasticity. Conclusions Our perspective allows for both a conceptual and quantitative description of system-level features of endothelial regulation. PMID:22723222
Terminal Dynamics Approach to Discrete Event Systems
NASA Technical Reports Server (NTRS)
Zak, Michail; Meyers, Ronald
1995-01-01
This paper presents and discusses a mathematical formalism for simulation of discrete event dynamic (DED)-a special type of 'man-made' systems to serve specific purposes of information processing. The main objective of this work is to demonstrate that the mathematical formalism for DED can be based upon a terminal model of Newtonian dynamics which allows one to relax Lipschitz conditions at some discrete points.!.
Uncertain dynamical systems: A differential game approach
NASA Technical Reports Server (NTRS)
Gutman, S.
1976-01-01
A class of dynamical systems in a conflict situation is formulated and discussed, and the formulation is applied to the study of an important class of systems in the presence of uncertainty. The uncertainty is deterministic and the only assumption is that its value belongs to a known compact set. Asymptotic stability is fully discussed with application to variable structure and model reference control systems.
Nonlinear dynamical system approaches towards neural prosthesis
Torikai, Hiroyuki; Hashimoto, Sho
2011-04-19
An asynchronous discrete-state spiking neurons is a wired system of shift registers that can mimic nonlinear dynamics of an ODE-based neuron model. The control parameter of the neuron is the wiring pattern among the registers and thus they are suitable for on-chip learning. In this paper an asynchronous discrete-state spiking neuron is introduced and its typical nonlinear phenomena are demonstrated. Also, a learning algorithm for a set of neurons is presented and it is demonstrated that the algorithm enables the set of neurons to reconstruct nonlinear dynamics of another set of neurons with unknown parameter values. The learning function is validated by FPGA experiments.
Subvisible cirrus clouds - a dynamical system approach
NASA Astrophysics Data System (ADS)
Spreitzer, Elisa Johanna; Patrik Marschalik, Manuel; Spichtinger, Peter
2017-06-01
Ice clouds, so-called cirrus clouds, occur very frequently in the tropopause region. A special class are subvisible cirrus clouds with an optical depth lower than 0.03, associated with very low ice crystal number concentrations. The dominant pathway for the formation of these clouds is not known well. It is often assumed that heterogeneous nucleation on solid aerosol particles is the preferred mechanism although homogeneous freezing of aqueous solution droplets might be possible, since these clouds occur in the low-temperature regime T < 235 K. For investigating subvisible cirrus clouds as formed by homogeneous freezing we develop a reduced cloud model from first principles, which is close enough to complex models but is also simple enough for mathematical analysis. The model consists of a three-dimensional set of ordinary differential equations, and includes the relevant processes as ice nucleation, diffusional growth and sedimentation. We study the formation and evolution of subvisible cirrus clouds in the low-temperature regime as driven by slow vertical updraughts (0 < w ≤ 0. 05 m s-1). The model is integrated numerically and also investigated by means of theory of dynamical systems. We found two qualitatively different states for the long-term behaviour of subvisible cirrus clouds. The first state is a stable focus; i.e. the solution of the differential equations performs damped oscillations and asymptotically reaches a constant value as an equilibrium state. The second state is a limit cycle in phase space; i.e. the solution asymptotically approaches a one-dimensional attractor with purely oscillatory behaviour. The transition between the states is characterised by a Hopf bifurcation and is determined by two parameters - vertical updraught velocity and temperature. In both cases, the properties of the simulated clouds agree reasonably well with simulations from a more detailed model, with former analytical studies, and with observations of subvisible cirrus
Cosmic infinity: a dynamical system approach
NASA Astrophysics Data System (ADS)
Bouhmadi-López, Mariam; Marto, João; Morais, João; Silva, César M.
2017-03-01
Dynamical system techniques are extremely useful to study cosmology. It turns out that in most of the cases, we deal with finite isolated fixed points corresponding to a given cosmological epoch. However, it is equally important to analyse the asymptotic behaviour of the universe. On this paper, we show how this can be carried out for 3-form models. In fact, we show that there are fixed points at infinity mainly by introducing appropriate compactifications and defining a new time variable that washes away any potential divergence of the system. The richness of 3-form models allows us as well to identify normally hyperbolic non-isolated fixed points. We apply this analysis to three physically interesting situations: (i) a pre-inflationary era; (ii) an inflationary era; (iii) the late-time dark matter/dark energy epoch.
Gustatory processing: a dynamic systems approach.
Jones, Lauren M; Fontanini, Alfredo; Katz, Donald B
2006-08-01
Recent gustatory studies have provided a growing body of evidence that taste processing is dynamic and distributed, and the taste system too complex to be adequately described by traditional feed-forward models of taste coding. Current research demonstrates that neuronal responses throughout the gustatory neuroaxis are broad, variable and temporally structured, as a result of the fact that the taste network is extensive and heavily interconnected, containing modulatory pathways, many of which are reciprocal. Multimodal influences (e.g. olfactory and somatosensory) and effects of internal state (e.g. attention and expectation), shown in both behavioral and neuronal responses to taste stimuli, add further complexity to neural taste responses. Future gustatory research should extend to more brain regions, incorporate more connections, and analyze behaviors and neuronal responses in both time- and state-dependent manners.
System identification based approach to dynamic weighing revisited
NASA Astrophysics Data System (ADS)
Niedźwiecki, Maciej; Meller, Michał; Pietrzak, Przemysław
2016-12-01
Dynamic weighing, i.e., weighing of objects in motion, without stopping them on the weighing platform, allows one to increase the rate of operation of automatic weighing systems, used in industrial production processes, without compromising their accuracy. Since the classical identification-based approach to dynamic weighing, based on the second-order mass-spring-damper model of the weighing system, does not yield satisfactory results when applied to conveyor belt type checkweighers, several extensions of this technique are examined. Experiments confirm that when appropriately modified the identification-based approach becomes a reliable tool for dynamic mass measurement in checkweighers.
An approach for characterizing coupling in dynamical systems
NASA Astrophysics Data System (ADS)
Janjarasjitt, S.; Loparo, K. A.
2008-10-01
The study of coupling in dynamical systems dates back to Christian Hyugens who, in 1665, discovered that pendulum clocks with the same length pendulum synchronize when they are near to each other. In that case the observed synchronous motion was out of phase. In this paper we propose a new approach for measuring the degree of coupling and synchronization of a dynamical system consisting of interacting subsystems. The measure is based on quantifying the active degrees of freedom (e.g. correlation dimension) of the coupled system and the constituent subsystems. The time-delay embedding scheme is extended to coupled systems and used for attractor reconstruction of the coupled dynamical system. We use the coupled Lorenz, Rossler and Hénon model systems with a coupling strength variable for evaluation of the proposed approach. Results show that we can measure the active degrees of freedom of the coupled dynamical systems and can quantify and distinguish the degree of synchronization or coupling in each of the dynamical systems studied. Furthermore, using this approach the direction of coupling can be determined.
An Analytical Dynamics Approach to the Control of Mechanical Systems
NASA Astrophysics Data System (ADS)
Mylapilli, Harshavardhan
A new and novel approach to the control of nonlinear mechanical systems is presented in this study. The approach is inspired by recent results in analytical dynamics that deal with the theory of constrained motion. The control requirements on the dynamical system are viewed from an analytical dynamics perspective and the theory of constrained motion is used to recast these control requirements as constraints on the dynamical system. Explicit closed form expressions for the generalized nonlinear control forces are obtained by using the fundamental equation of mechanics. The control so obtained is optimal at each instant of time and causes the constraints to be exactly satisfied. No linearizations and/or approximations of the nonlinear dynamical system are made, and no a priori structure is imposed on the nature of nonlinear controller. Three examples dealing with highly nonlinear complex dynamical systems that are chosen from diverse areas of discrete and continuum mechanics are presented to demonstrate the control approach. The first example deals with the energy control of underactuated inhomogeneous nonlinear lattices (or chains), the second example deals with the synchronization of the motion of multiple coupled slave gyros with that of a master gyro, and the final example deals with the control of incompressible hyperelastic rubber-like thin cantilever beams. Numerical simulations accompanying these examples show the ease, simplicity and the efficacy with which the control methodology can be applied and the accuracy with which the desired control objectives can be met.
Silicon-Neuron Design: A Dynamical Systems Approach
Arthur, John V.; Boahen, Kwabena
2010-01-01
We present an approach to design spiking silicon neurons based on dynamical systems theory. Dynamical systems theory aids in choosing the appropriate level of abstraction, prescribing a neuron model with the desired dynamics while maintaining simplicity. Further, we provide a procedure to transform the prescribed equations into subthreshold current-mode circuits. We present a circuit design example, a positive-feedback integrate-and-fire neuron, fabricated in 0.25 μm CMOS. We analyze and characterize the circuit, and demonstrate that it can be configured to exhibit desired behaviors, including spike-frequency adaptation and two forms of bursting. PMID:21617741
Letting Structure Emerge: Connectionist and Dynamical Systems Approaches to Cognition
McClelland, James L.; Botvinick, Matthew M.; Noelle, David C.; Plaut, David C.; Rogers, Timothy T.; Seidenberg, Mark S.; Smith, Linda B.
2011-01-01
Connectionist and dynamical systems approaches explain human thought, language and behavior in terms of the emergent consequences of a large number of simple non-cognitive processes. We view the entities that serve as the basis for structured probabilistic approaches as sometimes useful but often misleading abstractions that have no real basis in the actual processes that give rise to linguistic and cognitive abilities or the development of these abilities. While structured probabilistic approaches can be useful in determining what would be optimal under certain assumptions, we suggest that approaches such as the connectionist and dynamical systems approaches, which focus on explaining the mechanisms giving rise to cognition, will be essential in achieving a full understanding of cognition and development. PMID:20598626
Dynamical systems approaches to nonlinear problems in systems and circuits
Salam, F.M.A.; Levi, M.L.
1988-01-01
Applications of dynamical-systems analysis to nonlinear circuits and physical systems are discussed in reviews and reports. Topics addressed include general analytical methods, general simulation methods, nonlinear circuits and systems in electrical engineering, control systems, solids and vibrations, and mechanical systems. Consideration is given to the applicability of the Mel'nikov method to highly dissipative systems, damping in nonlinear solid mechanics, a three-dimensional rotation instrument for displaying strange attractors, a chaotic saddle catastrophe in forced oscillators, soliton experiments in annular Josephson junctions, local bifurcation control, periodic and chaotic motions of a buckled beam experiencing parametric and external excitation, and robust nonlinear computed torque control for robot manipulators.
A Constraint Generation Approach to Learning Stable Linear Dynamical Systems
2008-01-01
and † denotes the Moore - Penrose inverse . Eq. (3) asks Â to minimize the error in predicting the state at time t + 1 from the state at time t. Given...A Constraint Generation Approach to Learning Stable Linear Dynamical Systems Sajid M. Siddiqi Byron Boots Geoffrey J. Gordon January 2008...REPORT DATE JAN 2008 2. REPORT TYPE 3. DATES COVERED 00-00-2008 to 00-00-2008 4. TITLE AND SUBTITLE A Constraint Generation Approach to Learning
A decoupled recursive approach for constrained flexible multibody system dynamics
NASA Technical Reports Server (NTRS)
Lai, Hao-Jan; Kim, Sung-Soo; Haug, Edward J.; Bae, Dae-Sung
1989-01-01
A variational-vector calculus approach is employed to derive a recursive formulation for dynamic analysis of flexible multibody systems. Kinematic relationships for adjacent flexible bodies are derived in a companion paper, using a state vector notation that represents translational and rotational components simultaneously. Cartesian generalized coordinates are assigned for all body and joint reference frames, to explicitly formulate deformation kinematics under small deformation kinematics and an efficient flexible dynamics recursive algorithm is developed. Dynamic analysis of a closed loop robot is performed to illustrate efficiency of the algorithm.
Charting Multidisciplinary Team External Dynamics Using a Systems Thinking Approach
NASA Technical Reports Server (NTRS)
Barthelemy, Jean-Francois; Waszak, Martin R.; Jones, Kenneth M.; Silcox, Richard J.; Silva, Walter A.; Nowaczyk, Ronald H.
1998-01-01
Using the formalism provided by the Systems Thinking approach, the dynamics present when operating multidisciplinary teams are examined in the context of the NASA Langley Research and Technology Group, an R&D organization organized along functional lines. The paper focuses on external dynamics and examines how an organization creates and nurtures the teams and how it disseminates and retains the lessons and expertise created by the multidisciplinary activities. Key variables are selected and the causal relationships between the variables are identified. Five "stories" are told, each of which touches on a different aspect of the dynamics. The Systems Thinking Approach provides recommendations as to interventions that will facilitate the introduction of multidisciplinary teams and that therefore will increase the likelihood of performing successful multidisciplinary developments. These interventions can be carried out either by individual researchers, line management or program management.
Assessing the Dynamic Behavior of Online Q&A Knowledge Markets: A System Dynamics Approach
ERIC Educational Resources Information Center
Jafari, Mostafa; Hesamamiri, Roozbeh; Sadjadi, Jafar; Bourouni, Atieh
2012-01-01
Purpose: The objective of this paper is to propose a holistic dynamic model for understanding the behavior of a complex and internet-based kind of knowledge market by considering both social and economic interactions. Design/methodology/approach: A system dynamics (SD) model is formulated in this study to investigate the dynamic characteristics of…
Assessing the Dynamic Behavior of Online Q&A Knowledge Markets: A System Dynamics Approach
ERIC Educational Resources Information Center
Jafari, Mostafa; Hesamamiri, Roozbeh; Sadjadi, Jafar; Bourouni, Atieh
2012-01-01
Purpose: The objective of this paper is to propose a holistic dynamic model for understanding the behavior of a complex and internet-based kind of knowledge market by considering both social and economic interactions. Design/methodology/approach: A system dynamics (SD) model is formulated in this study to investigate the dynamic characteristics of…
The stochastic system approach for estimating dynamic treatments effect.
Commenges, Daniel; Gégout-Petit, Anne
2015-10-01
The problem of assessing the effect of a treatment on a marker in observational studies raises the difficulty that attribution of the treatment may depend on the observed marker values. As an example, we focus on the analysis of the effect of a HAART on CD4 counts, where attribution of the treatment may depend on the observed marker values. This problem has been treated using marginal structural models relying on the counterfactual/potential response formalism. Another approach to causality is based on dynamical models, and causal influence has been formalized in the framework of the Doob-Meyer decomposition of stochastic processes. Causal inference however needs assumptions that we detail in this paper and we call this approach to causality the "stochastic system" approach. First we treat this problem in discrete time, then in continuous time. This approach allows incorporating biological knowledge naturally. When working in continuous time, the mechanistic approach involves distinguishing the model for the system and the model for the observations. Indeed, biological systems live in continuous time, and mechanisms can be expressed in the form of a system of differential equations, while observations are taken at discrete times. Inference in mechanistic models is challenging, particularly from a numerical point of view, but these models can yield much richer and reliable results.
Tozan, Yesim; Ompad, Danielle C
2015-06-01
In a variety of urban health frameworks, cities are conceptualized as complex and dynamic yet commonly used epidemiological methods have failed to address this complexity and dynamism head on due to their narrow problem definitions and linear analytical representations. Scholars from a variety of disciplines have also long conceptualized cities as systems, but few have modeled urban health issues as problems within a system. Systems thinking in general and system dynamics in particular are relatively new approaches in public health, but ones that hold immense promise as methodologies to model and analyze the complexity underlying urban processes to effectively inform policy actions in dynamic environments. This conceptual essay reviews the utility of applying the concepts, principles, and methods of systems thinking to the study of complex urban health phenomena as a complementary approach to standard epidemiological methods using specific examples and provides recommendations on how to better incorporate systems thinking methods in urban health research and practice.
A Dynamical Systems Approach to Geodesics in Bianchi Cosmologies
NASA Astrophysics Data System (ADS)
Nilsson, Ulf S.; Uggla, Claes; Wainwright, John
2000-10-01
To understand the observational properties of cosmological models, in particular, the temperature of the cosmic microwave background radiation, it is necessary to study their null geodesics. Dynamical systems theory, in conjunction with the orthonormal frame approach, has proved to be an invaluable tool for analyzing spatially homogeneous cosmologies. It is thus natural to use such techniques to study the geodesics of these models. We therefore augment the Einstein field equations with the geodesic equations, all written in dimensionless form, obtaining an extended system of first-order ordinary differential equations that simultaneously describes the evolution of the gravitational field and the behavior of the associated geodesics. It is shown that the extended system is a powerful tool for investigating the effect of space-time anisotropies on the temperature of the cosmic microwave background radiation, and that it can also be used for studying geodesic chaos.
A variational approach to dynamics of flexible multibody systems
NASA Technical Reports Server (NTRS)
Wu, Shih-Chin; Haug, Edward J.; Kim, Sung-Soo
1989-01-01
This paper presents a variational formulation of constrained dynamics of flexible multibody systems, using a vector-variational calculus approach. Body reference frames are used to define global position and orientation of individual bodies in the system, located and oriented by position of its origin and Euler parameters, respectively. Small strain linear elastic deformation of individual components, relative to their body references frames, is defined by linear combinations of deformation modes that are induced by constraint reaction forces and normal modes of vibration. A library of kinematic couplings between flexible and/or rigid bodies is defined and analyzed. Variational equations of motion for multibody systems are obtained and reduced to mixed differential-algebraic equations of motion. A space structure that must deform during deployment is analyzed, to illustrate use of the methods developed.
A Dynamic Systems Approach to Internationalization of Higher Education
ERIC Educational Resources Information Center
Zhou, Jiangyuan
2016-01-01
Research shows that internationalization of higher education is a process rather than an end product. This paper applies the Dynamic Systems Theory to examine the nature and development of internationalization of higher education, and proposes that internationalization of higher education is a dynamic system. A dynamic framework of…
Iyengar, Srinivasan S; Jakowski, Jacek
2005-03-15
A methodology to efficiently conduct simultaneous dynamics of electrons and nuclei is presented. The approach involves quantum wave packet dynamics using an accurate banded, sparse and Toeplitz representation for the discrete free propagator, in conjunction with ab initio molecular dynamics treatment of the electronic and classical nuclear degree of freedom. The latter may be achieved either by using atom-centered density-matrix propagation or by using Born-Oppenheimer dynamics. The two components of the methodology, namely, quantum dynamics and ab initio molecular dynamics, are harnessed together using a time-dependent self-consistent field-like coupling procedure. The quantum wave packet dynamics is made computationally robust by using adaptive grids to achieve optimized sampling. One notable feature of the approach is that important quantum dynamical effects including zero-point effects, tunneling, as well as over-barrier reflections are treated accurately. The electronic degrees of freedom are simultaneously handled at accurate levels of density functional theory, including hybrid or gradient corrected approximations. Benchmark calculations are provided for proton transfer systems and the dynamics results are compared with exact calculations to determine the accuracy of the approach.
The Dynamic Systems Approach as Metatheory for Developmental Psychology
ERIC Educational Resources Information Center
Witherington, David C.
2007-01-01
The dynamic systems perspective has been touted as an integrative metatheoretical framework for the study of stability and change in development. However, two dynamic systems camps exist with respect to the role higher-order form, once emergent, plays in the process of development. This paper evaluates these two camps in terms of the overarching…
The Importance of Dynamic Systems Approaches for Understanding Development
ERIC Educational Resources Information Center
Howe, Mark L.; Lewis, Marc D.
2005-01-01
We outline the nature of dynamic systems, both linear and nonlinear, and we review dynamic systems principles that apply well to various aspects of human development, including the emergence of new forms, phases of stability and instability, continuous and discontinuous change, and differentiation among individual trajectories. We then document…
The Dynamic Systems Approach as Metatheory for Developmental Psychology
ERIC Educational Resources Information Center
Witherington, David C.
2007-01-01
The dynamic systems perspective has been touted as an integrative metatheoretical framework for the study of stability and change in development. However, two dynamic systems camps exist with respect to the role higher-order form, once emergent, plays in the process of development. This paper evaluates these two camps in terms of the overarching…
A system dynamics approach to understanding the One Health concept.
Xie, Tai; Liu, Wenbao; Anderson, Benjamin D; Liu, Xiaorong; Gray, Gregory C
2017-01-01
There have been many terms used to describe the One Health concept, including movement, strategy, framework, agenda, approach, among others. However, the inter-relationships of the disciplines engaged in the One Health concept have not been well described. To identify and better elucidate the internal feedback mechanisms of One Health, we employed a system dynamics approach. First, a systematic literature review was conducted via searches in PubMed, Web of Knowledge, and ProQuest with the search terms: 'One Health' and (concept* or approach*). In addition, we used the HistCite® tool to add significant articles on One Health to the library. Then, of the 2368 articles identified, 19 were selected for evaluating the inter-relationships of disciplines engaged in One Health. Herein, we report a visually rich, theoretical model regarding interactions of various disciplines and complex problem descriptors engaged in One Health problem solving. This report provides a conceptual framework for future descriptions of the interdisciplinary engagements involved in One Health.
Orbital approach to studying the slow dynamics of stellar systems
NASA Astrophysics Data System (ADS)
Polyachenko, V. L.; Polyachenko, E. V.; Shukhman, I. G.
2008-03-01
We develop new approaches to the numerical simulations of slowly evolving stellar systems with characteristic times of the order of the precession period for a typical orbit. This period is assumed to be long compared to the characteristic oscillation periods of individual stars in their orbits. For such processes, the standard numerical simulations using various N-body methods become inadequate, since the bulk of the computational time is spent on the repeated calculations of almost invariable orbits. We suggest a new N-orbit approach (called so by analogy and by contrast with N-body methods) that takes into account the specifics of the problems under consideration, in which whole orbits take the place of individual stars in N-body methods. Accordingly, the stellar system is represented by a set of N orbits the changes in the spatial orientation and shape of which lead to a slow evolution of the system. We derive the equations governing the nonlinear dynamics of orbits separately for 2D (disk) and 3D systems. These equations have the form of Hamiltonian equations for canonically conjugate pairs of variables. In the 2D case, one pair of such equations will suffice: for the angular momentum L and for the angle of direction to the apocenter Ψ. In the 3D case, there are two such pairs. The first pair of equations is for the modulus of the angular momentum L and the angle of direction to the apocenter in the orbital plane Ψ, while the second pair is for L z (the component of the angular momentum vector L along the z axis) and the orientation angle of the line of nodes W. Together with the energy E, which is an adiabatic invariant, these two (or four) parameters completely define the orbit (in the 2D and 3D cases, respectively). The evolution of the system is traced by solving these equations within the framework of the suggested N-orbit approach. We have in mind two versions of this approach. In the first version, a separate orbit corresponds to each star along which
Non-Lipschitz Dynamics Approach to Discrete Event Systems
NASA Technical Reports Server (NTRS)
Zak, M.; Meyers, R.
1995-01-01
This paper presents and discusses a mathematical formalism for simulation of discrete event dynamics (DED) - a special type of 'man- made' system designed to aid specific areas of information processing. A main objective is to demonstrate that the mathematical formalism for DED can be based upon the terminal model of Newtonian dynamics which allows one to relax Lipschitz conditions at some discrete points.
Quantum Dynamical Behaviour in Complex Systems - A Semiclassical Approach
Ananth, Nandini
2008-01-01
systems is described. We proposed the use of a semiclassical correction term to a preliminary quantum calculation using, for instance, a variational approach. This allows us to increase the accuracy significantly. Modeling Nonadiabatic dynamics has always been a challenge to classical simulations because the multi-state nature of the dynamics cannot be described accurately by the time evolution on a single average surface, as is the classical approach. We show that using the Meyer-Miller-Stock-Thoss (MMST) representation of the exact vibronic Hamiltonian in combination with the IVR allows us to accurately describe dynamics where the non Born-Oppenheimer regime. One final problem that we address is that of extending this method to the long time regime. We propose the use of a time independent sampling function in the Monte Carlo integration over the phase space of initial trajectory conditions. This allows us to better choose the regions of importance at the various points in time; by using more trajectories in the important regions, we show that the integration can be converged much easier. An algorithm based loosely on the methods of Diffusion Monte Carlo is developed that allows us to carry out this time dependent sampling in a most efficient manner.
Understanding ecohydrological connectivity in savannas: A system dynamics modeling approach
USDA-ARS?s Scientific Manuscript database
Ecohydrological connectivity is a system-level property that results from the linkages in the networks of water transport through ecosystems, by which feedback effects and other emergent system behaviors may be generated. We created a systems dynamic model that represents primary ecohydrological net...
ERIC Educational Resources Information Center
Howard, James E.
After identifying the components of a community college financial system as enrollment, costs, revenues and tuition, this paper addresses the need for a system dynamics analysis of a California community college district. This systems approach would assess the possible effects of alternative policies on the characteristic behavior modes of the…
Dynamical system approach to scalar-vector-tensor cosmology
NASA Astrophysics Data System (ADS)
Ghaffarnejad, H.; Yaraie, E.
2017-04-01
Using scalar-vector-tensor Brans Dicke (VBD) gravity (Ghaffarnejad in Gen Relativ Gravit 40:2229, 2008; Gen Relativ Gravit 41:2941, 2009) in presence of self interaction BD potential V(φ ) and perfect fluid matter field action we solve corresponding field equations via dynamical system approach for flat Friedmann Robertson Walker metric (FRW). We obtained three type critical points for Λ CDM vacuum de Sitter era where stability of our solutions are depended to choose particular values of BD parameter ω . One of these fixed points is supported by a constant potential which is stable for ω <0 and behaves as saddle (quasi stable) for ω ≥ 0. Two other ones are supported by a linear potential V(φ )˜ φ which one of them is stable for ω =0.27647. For a fixed value of ω there is at least 2 out of 3 critical points reaching to a unique critical point. Namely for ω =-0.16856(-0.56038) the second (third) critical point become unique with the first critical point. In dust and radiation eras we obtained one critical point which never become unique fixed point. In the latter case coordinates of fixed points are also depended to ω . To determine stability of our solutions we calculate eigenvalues of Jacobi matrix of 4D phase space dynamical field equations for de Sitter, dust and radiation eras. We should point also potentials which support dust and radiation eras must be similar to V(φ )˜ φ ^{-1/2} and V(φ )˜ φ ^{-1} respectively. In short our study predicts that radiation and dust eras of our VBD-FRW cosmology transmit to stable de Sitter state via non-constant potential (effective variable cosmological parameter) by choosing ω =0.27647.
Hybrid consensus protocols: an impulsive dynamical system approach
NASA Astrophysics Data System (ADS)
Hui, Qing
2010-06-01
In this article, we develop a novel hybrid control framework to address fast consensus seeking problems for multiagent dynamical systems. Specifically, we present hybrid distributed controller architectures for multiagent coordination to improve the transient performance of coordination tasks. The proposed controller architectures are predicated on some novel hybrid dynamic compensation structures involving the exchange of information between agents. A unique feature of the proposed framework is that the proposed controller architectures are hybrid and appear to achieve finite-time coordination, and hence significantly improve the transient performance of the closed-loop system. The overall closed-loop dynamics under any of these controller algorithms achieving consensus possesses discontinuous flows since the controller algorithms combine logical switchings with continuous dynamics, leading to impulsive differential equations. Several simulation results are provided to validate the proposed consensus protocols.
Modular and Spatially Explicit: A Novel Approach to System Dynamics
The Open Modeling Environment (OME) is an open-source System Dynamics (SD) simulation engine which has been created as a joint project between Oregon State University and the US Environmental Protection Agency. It is designed around a modular implementation, and provides a standa...
A System Dynamics Approach for Information Technology Implementation and Sustainment
2003-03-01
Kofron, and Richard Updike , for their financial support and superb system insight during the course of this research. I would also like to thank...Organizational Learning,” Sloan Management Review, Fall:37-50 (1993). 315 Kotter, John P. “Leading Change: Why Transformation Efforts Fail,” Harvard...Sterman, John D., Business Dynamics: Systems Thinking and Modeling for a Complex World, Kingport, McGraw-Hill Companies, Inc., 2000. Tornatzky
Dynamics and control of multibody systems: An approach with application
NASA Astrophysics Data System (ADS)
Grewal, A.; Modi, V. J.
1996-09-01
The paper focuses on the study of the dynamics and control of large flexible space structures, comprised of sub-assemblies, a subject of considerable contemporary interest. To begin with, a relatively general Lagrangian formulation of the problem is developed. The governing equations are non-linear, non-autonomous, coupled and extremely lengthy even in matrix notation. Next, an efficient computer code is developed and the versatility of the program illustrated through a study of the dynamics of the First Element Launch (FEL) configuration of the Space Station Freedom, now superseded by the International Space Station Alpha. The response of the FEL is obtained for two critical disturbances: (a) docking of the Space Shuttle; and (b) maneuver of the onboard mobile manipulator system (MSS). The study clearly demonstrates a need for active control. To that end, robust control of the rigid body motion of the FEL configuration using the LQG/LTR procedure is demonstrated. The controller designed using the simplified linear model, proves to be effective in regulating librational disturbances. Such a global approach—formulation, numerical code, dynamics and control—can serve as a powerful tool to gain comprehensive understanding of the interactions of the dynamics and thus aid in the development of effective and efficient control systems.
A dynamical systems approach to studying midlatitude weather extremes
NASA Astrophysics Data System (ADS)
Messori, Gabriele; Caballero, Rodrigo; Faranda, Davide
2017-04-01
Extreme weather occurrences carry enormous social and economic costs and routinely garner widespread scientific and media coverage. The ability to predict these events is therefore a topic of crucial importance. Here we propose a novel predictability pathway for extreme events, by building upon recent advances in dynamical systems theory. We show that simple dynamical systems metrics can be used to identify sets of large-scale atmospheric flow patterns with similar spatial structure and temporal evolution on time scales of several days to a week. In regions where these patterns favor extreme weather, they afford a particularly good predictability of the extremes. We specifically test this technique on the atmospheric circulation in the North Atlantic region, where it provides predictability of large-scale wintertime surface temperature extremes in Europe up to 1 week in advance.
A Global Approach to Parameter Estimation of Chaotic Dynamical Systems.
1992-12-01
ily of complex quadratic polynomials . We demonstrate how to exploit the complexity of global geometrical phase space structures of nonlinear 2.1 The...Quadratic Family dynamical systems and their dependence on parameter Given any complex quadratic polynomial p(:) = a:.! + variations in order to obtain...b•2 + r) tional maps obtained from Newton’s method on complex , 2 cubic polynomials . We show how to transform the esti- -(aZ + 2abz + b-’ + c) - b
Spatial operator approach to flexible multibody system dynamics and control
NASA Technical Reports Server (NTRS)
Rodriguez, G.
1991-01-01
The inverse and forward dynamics problems for flexible multibody systems were solved using the techniques of spatially recursive Kalman filtering and smoothing. These algorithms are easily developed using a set of identities associated with mass matrix factorization and inversion. These identities are easily derived using the spatial operator algebra developed by the author. Current work is aimed at computational experiments with the described algorithms and at modelling for control design of limber manipulator systems. It is also aimed at handling and manipulation of flexible objects.
Linear dynamic system approach to groundwater solute transport equation
Cho, W.C.
1984-01-01
Groundwater pollution in the United States has been recognized in the 1980's to be extensive both in degree and geographic distribution. It has been recognized that in many cases groundwater pollution is essentially irreversible from the engineering or economic viewpoint. Under the best circumstance the problem is complicated by insufficient amounts of field data which is costly to obtain. In general, the governing partial differential equation of solute transport is spatially discretized either using finite difference or finite element scheme. The time derivative is also approximated by finite difference. In this study, only the spatial discretization is performed using finite element method and the time derivative is retained in continuous form. The advantage is that special features of finite element are maintained but most important of all is that the equation can be rearranged to be in a standard form of linear dynamic system. Two problems were studied in detail: one is the determination of the locatio of groundwater pollution source(s). The problem is equivalent to identifying an input to the dynamic system and is solved by using the sensitivity theorem. The other one is the prediction of pollutant concentration at a given time at a given location. The eigenvalue technique was employed to solve this problem and the detailed procedures of the computation were delineated.
NASA Astrophysics Data System (ADS)
Pasqualini, D.; Witkowski, M.
2005-12-01
The Critical Infrastructure Protection / Decision Support System (CIP/DSS) project, supported by the Science and Technology Office, has been developing a risk-informed Decision Support System that provides insights for making critical infrastructure protection decisions. The system considers seventeen different Department of Homeland Security defined Critical Infrastructures (potable water system, telecommunications, public health, economics, etc.) and their primary interdependencies. These infrastructures have been modeling in one model called CIP/DSS Metropolitan Model. The modeling approach used is a system dynamics modeling approach. System dynamics modeling combines control theory and the nonlinear dynamics theory, which is defined by a set of coupled differential equations, which seeks to explain how the structure of a given system determines its behavior. In this poster we present a system dynamics model for one of the seventeen critical infrastructures, a generic metropolitan potable water system (MPWS). Three are the goals: 1) to gain a better understanding of the MPWS infrastructure; 2) to identify improvements that would help protect MPWS; and 3) to understand the consequences, interdependencies, and impacts, when perturbations occur to the system. The model represents raw water sources, the metropolitan water treatment process, storage of treated water, damage and repair to the MPWS, distribution of water, and end user demand, but does not explicitly represent the detailed network topology of an actual MPWS. The MPWS model is dependent upon inputs from the metropolitan population, energy, telecommunication, public health, and transportation models as well as the national water and transportation models. We present modeling results and sensitivity analysis indicating critical choke points, negative and positive feedback loops in the system. A general scenario is also analyzed where the potable water system responds to a generic disruption.
General approach for dealing with dynamical systems with spatiotemporal periodicities.
Casado-Pascual, Jesús; Cuesta, José A; Quintero, Niurka R; Alvarez-Nodarse, Renato
2015-02-01
Dynamical systems often contain oscillatory forces or depend on periodic potentials. Time or space periodicity is reflected in the properties of these systems through a dependence on the parameters of their periodic terms. In this paper we provide a general theoretical framework for dealing with these kinds of systems, regardless of whether they are classical or quantum, stochastic or deterministic, dissipative or nondissipative, linear or nonlinear, etc. In particular, we are able to show that simple symmetry considerations determine, to a large extent, how their properties depend functionally on some of the parameters of the periodic terms. For the sake of illustration, we apply this formalism to find the functional dependence of the expectation value of the momentum of a Bose-Einstein condensate, described by the Gross-Pitaewskii equation, when it is exposed to a sawtooth potential whose amplitude is periodically modulated in time. We show that, by using this formalism, a small set of measurements is enough to obtain the functional form for a wide range of parameters. This can be very helpful when characterizing experimentally the response of systems for which performing measurements is costly or difficult.
Adsorbed polymers under flow. A stochastic dynamical system approach
NASA Astrophysics Data System (ADS)
Armstrong, Robert; Jhon, Myung S.
1985-09-01
Recent experiments have shown that porous filters preadsorbed with polymer molecules exhibit an anomalously high pressure drop at high rates of flow. We have modeled the adsorbed polymers as dynamical systems and have found that the introduction of hydrodynamic interaction between molecules destabilizes at a high applied shear. As a direct result this instability will cause the molecules to unravel and stretch far into the cross section of the pore, and thus by inference, cause the observed anomalously high pressure drop. Although much of this paper is devoted to the stability characteristics of the deterministic system, Brownian motion is also considered, and an account of the statistics of the Brownian system when the deterministic system becomes unstable is given. The examples revealed in this paper are not of sufficient complexity to calculate with any accuracy the magnitude of this anomalous pressure drop. We simply present a procedure by which a large variety of more complex models could be undertaken and their ultimate effect clearly understood.
Complex systems approach to fire dynamics and climate change impacts
NASA Astrophysics Data System (ADS)
Pueyo, S.
2012-04-01
I present some recent advances in complex systems theory as a contribution to understanding fire regimes and forecasting their response to a changing climate, qualitatively and quantitatively. In many regions of the world, fire sizes have been found to follow, approximately, a power-law frequency distribution. As noted by several authors, this distribution also arises in the "forest fire" model used by physicists to study mechanisms that give rise to scale invariance (the power law is a scale-invariant distribution). However, this model does not give and does not pretend to give a realistic description of fire dynamics. For example, it gives no role to weather and climate. Pueyo (2007) developed a variant of the "forest fire" model that is also simple but attempts to be more realistic. It also results into a power law, but the parameters of this distribution change through time as a function of weather and climate. Pueyo (2007) observed similar patterns of response to weather in data from boreal forest fires, and used the fitted response functions to forecast fire size distributions in a possible climate change scenario, including the upper extreme of the distribution. For some parameter values, the model in Pueyo (2007) displays a qualitatively different behavior, consisting of simple percolation. In this case, fire is virtually absent, but megafires sweep through the ecosystem a soon as environmental forcings exceed a critical threshold. Evidence gathered by Pueyo et al. (2010) suggests that this is realistic for tropical rainforests (specifically, well-conserved upland rainforests). Some climate models suggest that major tropical rainforest regions are going to become hotter and drier if climate change goes ahead unchecked, which could cause such abrupt shifts. Not all fire regimes are well described by this model. Using data from a tropical savanna region, Pueyo et al. (2010) found that the dynamics in this area do not match its assumptions, even though fire
Solar System dynamics, beyond the two-body-problem approach
NASA Astrophysics Data System (ADS)
Varvoglis, Harry
2006-08-01
When one thinks of the solar system, he has usually in mind the picture based on the solution of the two-body problem approximation presented by Newton, namely the ordered clockwork motion of planets on fixed, non-intersecting orbits around the Sun. However, already by the end of the 18th century this picture was proven to be wrong. As discussed by Laplace and Lagrange (for a modern approach see [3] or [2]), the interaction between the various planets leads to secular changes in their orbits, which nevertheless were believed to be corrections of higher order to the Keplerian elliptical motion. This idea has changed completely the last decades. Now it is well know that the solar system was created from a state of chaotic interactions of planetesimals, primordial bodies the size of a small asteroid, and that since this time many episodes of cataclysmic collisions have shaken all major planets, due to the pronounced chaotic motion of the minor bodies. A new discipline has emerged out of the above new ideas, which is based on the statistical approach to chaotic motion of bodies, in particular those in the asteroid belt. At the same time it has been understood that non-gravitational forces, in particular the Yarkovsky effect, may play an important role on the long-time evolution of the trajectories of kilometer-sized bodies.
Extreme event statistics of daily rainfall: dynamical systems approach
NASA Astrophysics Data System (ADS)
Cigdem Yalcin, G.; Rabassa, Pau; Beck, Christian
2016-04-01
We analyse the probability densities of daily rainfall amounts at a variety of locations on Earth. The observed distributions of the amount of rainfall fit well to a q-exponential distribution with exponent q close to q≈ 1.3. We discuss possible reasons for the emergence of this power law. In contrast, the waiting time distribution between rainy days is observed to follow a near-exponential distribution. A careful investigation shows that a q-exponential with q≈ 1.05 yields the best fit of the data. A Poisson process where the rate fluctuates slightly in a superstatistical way is discussed as a possible model for this. We discuss the extreme value statistics for extreme daily rainfall, which can potentially lead to flooding. This is described by Fréchet distributions as the corresponding distributions of the amount of daily rainfall decay with a power law. Looking at extreme event statistics of waiting times between rainy days (leading to droughts for very long dry periods) we obtain from the observed near-exponential decay of waiting times extreme event statistics close to Gumbel distributions. We discuss superstatistical dynamical systems as simple models in this context.
A self-cognizant dynamic system approach for prognostics and health management
NASA Astrophysics Data System (ADS)
Bai, Guangxing; Wang, Pingfeng; Hu, Chao
2015-03-01
Prognostics and health management (PHM) is an emerging engineering discipline that diagnoses and predicts how and when a system will degrade its performance and lose its partial or whole functionality. Due to the complexity and invisibility of rules and states of most dynamic systems, developing an effective approach to track evolving system states becomes a major challenge. This paper presents a new self-cognizant dynamic system (SCDS) approach that incorporates artificial intelligence into dynamic system modeling for PHM. A feed-forward neural network (FFNN) is selected to approximate a complex system response which is challenging task in general due to inaccessible system physics. The trained FFNN model is then embedded into a dual extended Kalman filter algorithm to track down system dynamics. A recursive computation technique used to update the FFNN model using online measurements is also derived. To validate the proposed SCDS approach, a battery dynamic system is considered as an experimental application. After modeling the battery system by a FFNN model and a state-space model, the state-of-charge (SoC) and state-of-health (SoH) are estimated by updating the FFNN model using the proposed approach. Experimental results suggest that the proposed approach improves the efficiency and accuracy for battery health management.
Statistical physics approaches to subnetwork dynamics in biochemical systems
NASA Astrophysics Data System (ADS)
Bravi, B.; Sollich, P.
2017-08-01
We apply a Gaussian variational approximation to model reduction in large biochemical networks of unary and binary reactions. We focus on a small subset of variables (subnetwork) of interest, e.g. because they are accessible experimentally, embedded in a larger network (bulk). The key goal is to write dynamical equations reduced to the subnetwork but still retaining the effects of the bulk. As a result, the subnetwork-reduced dynamics contains a memory term and an extrinsic noise term with non-trivial temporal correlations. We first derive expressions for this memory and noise in the linearized (Gaussian) dynamics and then use a perturbative power expansion to obtain first order nonlinear corrections. For the case of vanishing intrinsic noise, our description is explicitly shown to be equivalent to projection methods up to quadratic terms, but it is applicable also in the presence of stochastic fluctuations in the original dynamics. An example from the epidermal growth factor receptor signalling pathway is provided to probe the increased prediction accuracy and computational efficiency of our method.
Dynamical systems approach and generic properties of f (T ) cosmology
NASA Astrophysics Data System (ADS)
Hohmann, Manuel; Järv, Laur; Ualikhanova, Ulbossyn
2017-08-01
We present a systematic analysis of the dynamics of flat Friedmann-Lemaître-Robertson-Walker cosmological models with radiation and dust matter in generalized teleparallel f (T ) gravity. We show that the cosmological dynamics of this model are fully described by a function W (H ) of the Hubble parameter, which is constructed from the function f (T ) . After reducing the phase space to two dimensions, we derive the conditions on W (H ) for the occurrence of de Sitter fixed points, accelerated expansion, crossing the phantom divide, and finite time singularities. Depending on the model parameters, it is possible to have a bounce (from contraction to expansion) or a turnaround (from expansion to contraction), but cyclic or oscillating scenarios are prohibited. As an illustration of the formalism we consider power law f (T )=T +α (-T )n models, and show that these allow only one period of acceleration and no phantom divide crossing.
Two dissimilar approaches to dynamical systems on hyper MV -algebras and their information entropy
NASA Astrophysics Data System (ADS)
Mehrpooya, Adel; Ebrahimi, Mohammad; Davvaz, Bijan
2017-09-01
Measuring the flow of information that is related to the evolution of a system which is modeled by applying a mathematical structure is of capital significance for science and usually for mathematics itself. Regarding this fact, a major issue in concern with hyperstructures is their dynamics and the complexity of the varied possible dynamics that exist over them. Notably, the dynamics and uncertainty of hyper MV -algebras which are hyperstructures and extensions of a central tool in infinite-valued Lukasiewicz propositional calculus that models many valued logics are of primary concern. Tackling this problem, in this paper we focus on the subject of dynamical systems on hyper MV -algebras and their entropy. In this respect, we adopt two varied approaches. One is the set-based approach in which hyper MV -algebra dynamical systems are developed by employing set functions and set partitions. By the other method that is based on points and point partitions, we establish the concept of hyper injective dynamical systems on hyper MV -algebras. Next, we study the notion of entropy for both kinds of systems. Furthermore, we consider essential ergodic characteristics of those systems and their entropy. In particular, we introduce the concept of isomorphic hyper injective and hyper MV -algebra dynamical systems, and we demonstrate that isomorphic systems have the same entropy. We present a couple of theorems in order to help calculate entropy. In particular, we prove a contemporary version of addition and Kolmogorov-Sinai Theorems. Furthermore, we provide a comparison between the indispensable properties of hyper injective and semi-independent dynamical systems. Specifically, we present and prove theorems that draw comparisons between the entropies of such systems. Lastly, we discuss some possible relationships between the theories of hyper MV -algebra and MV -algebra dynamical systems.
The dynamic systems approach to control and regulation of intracellular networks.
Wolkenhauer, Olaf; Ullah, Mukhtar; Wellstead, Peter; Cho, Kwang-Hyun
2005-03-21
Systems theory and cell biology have enjoyed a long relationship that has received renewed interest in recent years in the context of systems biology. The term 'systems' in systems biology comes from systems theory or dynamic systems theory: systems biology is defined through the application of systems- and signal-oriented approaches for an understanding of inter- and intra-cellular dynamic processes. The aim of the present text is to review the systems and control perspective of dynamic systems. The biologist's conceptual framework for representing the variables of a biochemical reaction network, and for describing their relationships, are pathway maps. A principal goal of systems biology is to turn these static maps into dynamic models, which can provide insight into the temporal evolution of biochemical reaction networks. Towards this end, we review the case for differential equation models as a 'natural' representation of causal entailment in pathways. Block-diagrams, commonly used in the engineering sciences, are introduced and compared to pathway maps. The stimulus-response representation of a molecular system is a necessary condition for an understanding of dynamic interactions among the components that make up a pathway. Using simple examples, we show how biochemical reactions are modelled in the dynamic systems framework and visualized using block-diagrams.
On the sighting of unicorns: A variational approach to computing invariant sets in dynamical systems
NASA Astrophysics Data System (ADS)
Junge, Oliver; Kevrekidis, Ioannis G.
2017-06-01
We propose to compute approximations to invariant sets in dynamical systems by minimizing an appropriate distance between a suitably selected finite set of points and its image under the dynamics. We demonstrate, through computational experiments, that this approach can successfully converge to approximations of (maximal) invariant sets of arbitrary topology, dimension, and stability, such as, e.g., saddle type invariant sets with complicated dynamics. We further propose to extend this approach by adding a Lennard-Jones type potential term to the objective function, which yields more evenly distributed approximating finite point sets, and illustrate the procedure through corresponding numerical experiments.
A spectral approach for damage quantification in stochastic dynamic systems
NASA Astrophysics Data System (ADS)
Machado, M. R.; Adhikari, S.; Santos, J. M. C. Dos
2017-05-01
Intrinsic to all real structures, parameter uncertainty can be found in material properties and geometries. Many structural parameters, such as, elastic modulus, Poisson's rate, thickness, density, etc., are spatially distributed by nature. The Karhunen-Loève expansion is a method used to model the random field expanded in a spectral decomposition. Once many structural parameters can not be modelled as a Gaussian distribution the memoryless nonlinear transformation is used to translate a Gaussian random field in a non-Gaussian. Thus, stochastic methods have been used to include these uncertainties in the structural model. The Spectral Element Method (SEM) is a wave-based numerical approach used to model structures. It is also developed to express parameters as spatially correlated random field in its formulation. In this paper, the problem of structural damage detection under the presence of spatially distributed random parameter is addressed. Explicit equations to localize and assess damage are proposed based on the SEM formulation. Numerical examples in an axially vibrating undamaged and damaged structure with distributed parameters are analysed.
Pant, Sanjay; Lombardi, Damiano
2015-10-01
A new approach for assessing parameter identifiability of dynamical systems in a Bayesian setting is presented. The concept of Shannon entropy is employed to measure the inherent uncertainty in the parameters. The expected reduction in this uncertainty is seen as the amount of information one expects to gain about the parameters due to the availability of noisy measurements of the dynamical system. Such expected information gain is interpreted in terms of the variance of a hypothetical measurement device that can measure the parameters directly, and is related to practical identifiability of the parameters. If the individual parameters are unidentifiable, correlation between parameter combinations is assessed through conditional mutual information to determine which sets of parameters can be identified together. The information theoretic quantities of entropy and information are evaluated numerically through a combination of Monte Carlo and k-nearest neighbour methods in a non-parametric fashion. Unlike many methods to evaluate identifiability proposed in the literature, the proposed approach takes the measurement-noise into account and is not restricted to any particular noise-structure. Whilst computationally intensive for large dynamical systems, it is easily parallelisable and is non-intrusive as it does not necessitate re-writing of the numerical solvers of the dynamical system. The application of such an approach is presented for a variety of dynamical systems--ranging from systems governed by ordinary differential equations to partial differential equations--and, where possible, validated against results previously published in the literature.
NASA Astrophysics Data System (ADS)
Morecroft, John
System dynamics is an approach for thinking about and simulating situations and organisations of all kinds and sizes by visualising how the elements fit together, interact and change over time. This chapter, written by John Morecroft, describes modern system dynamics which retains the fundamentals developed in the 1950s by Jay W. Forrester of the MIT Sloan School of Management. It looks at feedback loops and time delays that affect system behaviour in a non-linear way, and illustrates how dynamic behaviour depends upon feedback loop structures. It also recognises improvements as part of the ongoing process of managing a situation in order to achieve goals. Significantly it recognises the importance of context, and practitioner skills. Feedback systems thinking views problems and solutions as being intertwined. The main concepts and tools: feedback structure and behaviour, causal loop diagrams, dynamics, are practically illustrated in a wide variety of contexts from a hot water shower through to a symphony orchestra and the practical application of the approach is described through several real examples of its use for strategic planning and evaluation.
Galitski, Victor
2011-07-15
We propose a Lie-algebraic duality approach to analyze nonequilibrium evolution of closed dynamical systems and thermodynamics of interacting quantum lattice models (formulated in terms of Hubbard-Stratonovich dynamical systems). The first part of the paper utilizes a geometric Hilbert-space-invariant formulation of unitary time evolution, where a quantum Hamiltonian is viewed as a trajectory in an abstract Lie algebra, while the sought-after evolution operator is a trajectory in a dynamic group, generated by the algebra via exponentiation. The evolution operator is uniquely determined by the time-dependent dual generators that satisfy a system of differential equations, dubbed here dual Schroedinger-Bloch equations, which represent a viable alternative to the conventional Schroedinger formulation. These dual Schroedinger-Bloch equations are derived and analyzed on a number of specific examples. It is shown that deterministic dynamics of a closed classical dynamical system occurs as action of a symmetry group on a classical manifold and is driven by the same dual generators as in the corresponding quantum problem. This represents quantum-to-classical correspondence. In the second part of the paper, we further extend the Lie-algebraic approach to a wide class of interacting many-particle lattice models. A generalized Hubbard-Stratonovich transform is proposed and it is used to show that the thermodynamic partition function of a generic many-body quantum lattice model can be expressed in terms of traces of single-particle evolution operators governed by the dynamic Hubbard-Stratonovich fields. The corresponding Hubbard-Stratonovich dynamical systems are generally nonunitary, which yields a number of notable complications, including breakdown of the global exponential representation. Finally, we derive Hubbard-Stratonovich dynamical systems for the Bose-Hubbard model and a quantum spin model and use the Lie-algebraic approach to obtain new nonperturbative dual
Controlling aliased dynamics in motion systems? An identification for sampled-data control approach
NASA Astrophysics Data System (ADS)
Oomen, Tom
2014-07-01
Sampled-data control systems occasionally exhibit aliased resonance phenomena within the control bandwidth. The aim of this paper is to investigate the aspect of these aliased dynamics with application to a high performance industrial nano-positioning machine. This necessitates a full sampled-data control design approach, since these aliased dynamics endanger both the at-sample performance and the intersample behaviour. The proposed framework comprises both system identification and sampled-data control. In particular, the sampled-data control objective necessitates models that encompass the intersample behaviour, i.e., ideally continuous time models. Application of the proposed approach on an industrial wafer stage system provides a thorough insight and new control design guidelines for controlling aliased dynamics.
a Statistical Dynamic Approach to Structural Evolution of Complex Capital Market Systems
NASA Astrophysics Data System (ADS)
Shao, Xiao; Chai, Li H.
As an important part of modern financial systems, capital market has played a crucial role on diverse social resource allocations and economical exchanges. Beyond traditional models and/or theories based on neoclassical economics, considering capital markets as typical complex open systems, this paper attempts to develop a new approach to overcome some shortcomings of the available researches. By defining the generalized entropy of capital market systems, a theoretical model and nonlinear dynamic equation on the operations of capital market are proposed from statistical dynamic perspectives. The US security market from 1995 to 2001 is then simulated and analyzed as a typical case. Some instructive results are discussed and summarized.
ERIC Educational Resources Information Center
Witherington, David C.
2011-01-01
The dynamic systems (DS) approach has emerged as an influential and potentially unifying metatheory for developmental science. Its central platform--the argument against design--suggests that structure spontaneously and without prescription emerges through self-organization. In one of the most prominent accounts of DS, Thelen and her colleagues…
The Promise of Dynamic Systems Approaches for an Integrated Account of Human Development.
ERIC Educational Resources Information Center
Lewis, Marc D.
2000-01-01
Argues that dynamic systems approaches may provide an explanatory framework based on general scientific principles for developmental psychology, using principles of self-organization to explain how novel forms emerge without predetermination and become increasingly complex with development. Contends that self-organization provides a single…
When do perturbative approaches accurately capture the dynamics of complex quantum systems?
Fruchtman, Amir; Lambert, Neill; Gauger, Erik M.
2016-01-01
Understanding the dynamics of higher-dimensional quantum systems embedded in a complex environment remains a significant theoretical challenge. While several approaches yielding numerically converged solutions exist, these are computationally expensive and often provide only limited physical insight. Here we address the question: when do more intuitive and simpler-to-compute second-order perturbative approaches provide adequate accuracy? We develop a simple analytical criterion and verify its validity for the case of the much-studied FMO dynamics as well as the canonical spin-boson model. PMID:27335176
Dynamical systems approach to one-dimensional spatiotemporal chaos: A cyclist's view
NASA Astrophysics Data System (ADS)
Lan, Yueheng
We propose a dynamical systems approach to the study of weak turbulence (spatiotemporal chaos) based on the periodic orbit theory, emphasizing the role of recurrent patterns and coherent structures. After a brief review of the periodic orbit theory and its application to low-dimensional dynamics, we discuss its possible extension to study dynamics of spatially extended systems. The discussion is three-fold. First, we introduce a novel variational scheme for finding periodic orbits in high-dimensional systems. Second, we prove rigorously the existence of periodic structures (modulated amplitude waves) near the first instability of the complex Ginzburg-Landau equation, and check their role in pattern formation. Third, we present the extensive numerical exploration of the Kuramoto-Sivashinsky system in the chaotic regime: structure of the equilibrium solutions, our search for the shortest periodic orbits, description of the chaotic invariant set in terms of intrinsic coordinates and return maps on the Poincare section.
Rolfe, Bryan A.; Chun, Jaehun; Joo, Yong L.
2013-09-05
Recent experimental work has shown that polymeric micelles can template nanoparticles via interstitial sites in shear-ordered micelle solutions. In the current study, we report simulation results based on a coarse-grained molecular dynamics (CGMD) model of a solvent/polymer/nanoparticle system. Our results demonstrate the importance of polymer concentration and the micelle corona length in 2D shear-ordering of neat block copolymer solutions. Although our results do not show strong 3D ordering during shear, we find that cessation of shear allows the system to relax into a 3D configuration of greater order than without shear. It is further shown that this post-shear relaxation is strongly dependent on the length of the micelle corona. For the first time, we demonstrate the presence and importance of a flow disturbance surrounding micelles in simple shear flow at moderate Péclet numbers. This disturbance is similar to what is observed around simulated star polymers and ellipsoids. The extent of the flow disturbance increases as expected with a longer micelle corona length. It is further suggested that without proper consideration of these dynamics, a stable nanoparticle configuration would be difficult to obtain.
Design an optimum safety policy for personnel safety management - A system dynamic approach
NASA Astrophysics Data System (ADS)
Balaji, P.
2014-10-01
Personnel safety management (PSM) ensures that employee's work conditions are healthy and safe by various proactive and reactive approaches. Nowadays it is a complex phenomenon because of increasing dynamic nature of organisations which results in an increase of accidents. An important part of accident prevention is to understand the existing system properly and make safety strategies for that system. System dynamics modelling appears to be an appropriate methodology to explore and make strategy for PSM. Many system dynamics models of industrial systems have been built entirely for specific host firms. This thesis illustrates an alternative approach. The generic system dynamics model of Personnel safety management was developed and tested in a host firm. The model was undergone various structural, behavioural and policy tests. The utility and effectiveness of model was further explored through modelling a safety scenario. In order to create effective safety policy under resource constraint, DOE (Design of experiment) was used. DOE uses classic designs, namely, fractional factorials and central composite designs. It used to make second order regression equation which serve as an objective function. That function was optimized under budget constraint and optimum value used for safety policy which shown greatest improvement in overall PSM. The outcome of this research indicates that personnel safety management model has the capability for acting as instruction tool to improve understanding of safety management and also as an aid to policy making.
Design an optimum safety policy for personnel safety management - A system dynamic approach
Balaji, P.
2014-10-06
Personnel safety management (PSM) ensures that employee's work conditions are healthy and safe by various proactive and reactive approaches. Nowadays it is a complex phenomenon because of increasing dynamic nature of organisations which results in an increase of accidents. An important part of accident prevention is to understand the existing system properly and make safety strategies for that system. System dynamics modelling appears to be an appropriate methodology to explore and make strategy for PSM. Many system dynamics models of industrial systems have been built entirely for specific host firms. This thesis illustrates an alternative approach. The generic system dynamics model of Personnel safety management was developed and tested in a host firm. The model was undergone various structural, behavioural and policy tests. The utility and effectiveness of model was further explored through modelling a safety scenario. In order to create effective safety policy under resource constraint, DOE (Design of experiment) was used. DOE uses classic designs, namely, fractional factorials and central composite designs. It used to make second order regression equation which serve as an objective function. That function was optimized under budget constraint and optimum value used for safety policy which shown greatest improvement in overall PSM. The outcome of this research indicates that personnel safety management model has the capability for acting as instruction tool to improve understanding of safety management and also as an aid to policy making.
Dynamic analysis of flexible rotor-bearing systems using a modal approach
NASA Technical Reports Server (NTRS)
Choy, K. C.; Gunter, E. J.; Barrett, L. E.
1978-01-01
The generalized dynamic equations of motion were obtained by the direct stiffness method for multimass flexible rotor-bearing systems. The direct solution of the equations of motion is illustrated on a simple 3-mass system. For complex rotor-bearing systems, the direct solution of the equations becomes very difficult. The transformation of the equations of motion into modal coordinates can greatly simplify the computation for the solution. The use of undamped and damped system mode shapes in the transformation are discussed. A set of undamped critical speed modes is used to transform the equations of motion into a set of coupled modal equations of motion. A rapid procedure for computing stability, steady state unbalance response, and transient response of the rotor-bearing system is presented. Examples of the application of this modal approach are presented. The dynamics of the system is further investigated with frequency spectrum analysis of the transient response.
Computational dynamic approaches for temporal omics data with applications to systems medicine.
Liang, Yulan; Kelemen, Arpad
2017-01-01
Modeling and predicting biological dynamic systems and simultaneously estimating the kinetic structural and functional parameters are extremely important in systems and computational biology. This is key for understanding the complexity of the human health, drug response, disease susceptibility and pathogenesis for systems medicine. Temporal omics data used to measure the dynamic biological systems are essentials to discover complex biological interactions and clinical mechanism and causations. However, the delineation of the possible associations and causalities of genes, proteins, metabolites, cells and other biological entities from high throughput time course omics data is challenging for which conventional experimental techniques are not suited in the big omics era. In this paper, we present various recently developed dynamic trajectory and causal network approaches for temporal omics data, which are extremely useful for those researchers who want to start working in this challenging research area. Moreover, applications to various biological systems, health conditions and disease status, and examples that summarize the state-of-the art performances depending on different specific mining tasks are presented. We critically discuss the merits, drawbacks and limitations of the approaches, and the associated main challenges for the years ahead. The most recent computing tools and software to analyze specific problem type, associated platform resources, and other potentials for the dynamic trajectory and interaction methods are also presented and discussed in detail.
Gelo, Omar Carlo Gioacchino; Salvatore, Sergio
2016-07-01
Notwithstanding the many methodological advances made in the field of psychotherapy research, at present a metatheoretical, school-independent framework to explain psychotherapy change processes taking into account their dynamic and complex nature is still lacking. Over the last years, several authors have suggested that a dynamic systems (DS) approach might provide such a framework. In the present paper, we review the main characteristics of a DS approach to psychotherapy. After an overview of the general principles of the DS approach, we describe the extent to which psychotherapy can be considered as a self-organizing open complex system, whose developmental change processes are described in terms of a dialectic dynamics between stability and change over time. Empirical evidence in support of this conceptualization is provided and discussed. Finally, we propose a research design strategy for the empirical investigation of psychotherapy from a DS approach, together with a research case example. We conclude that a DS approach may provide a metatheoretical, school-independent framework allowing us to constructively rethink and enhance the way we conceptualize and empirically investigate psychotherapy. (PsycINFO Database Record (c) 2016 APA, all rights reserved).
Modeling Spring Mass System with System Dynamics Approach in Middle School Education
ERIC Educational Resources Information Center
Nuhoglu, Hasret
2008-01-01
System Dynamics is a well formulated methodology for analyzing the components of a system including causeeffect relationships and their underlying mathematics and logic, time delays, and feedback loops. It began in the business and manufacturing world, but is now affecting education and many other disciplines. Having inspired by successful policy…
Modeling Spring Mass System with System Dynamics Approach in Middle School Education
ERIC Educational Resources Information Center
Nuhoglu, Hasret
2008-01-01
System Dynamics is a well formulated methodology for analyzing the components of a system including cause-effect relationships and their underlying mathematics and logic, time delays, and feedback loops. It began in the business and manufacturing world, but is now affecting education and many other disciplines. Having inspired by successful policy…
A system dynamics approach to intermodalism at the Port of Lewiston
Sebo, D.
1996-08-01
Intermodalism refers to interconnections among modes of transportation, e.g., road, rail, water, and air. Effective intermodal planning must cross boundaries between the public and private sectors as well as transportation modes. The development of an effective and efficient intermodal transportation system requires the identification of barriers to intermodal transportation and the investigation of the impact of proposed changes in infrastructure development, policies, regulations, and planning. A systems approach is necessary to adequately represent the interaction between the sometimes incompatible concerns of all modes and stakeholders. A systems dynamics model of intermodalism at the Port of Lewiston has been developed to highlight leverage points, hidden assumptions, second order effects resulting from feedback loops and system drivers. The purpose of this document is to present the results of the system dynamics model work.
Nonadiabatic Molecular Dynamics for Thousand Atom Systems: A Tight-Binding Approach toward PYXAID.
Pal, Sougata; Trivedi, Dhara J; Akimov, Alexey V; Aradi, Bálint; Frauenheim, Thomas; Prezhdo, Oleg V
2016-04-12
Excited state dynamics at the nanoscale requires treatment of systems involving hundreds and thousands of atoms. In the majority of cases, depending on the process under investigation, the electronic structure component of the calculation constitutes the computation bottleneck. We developed an efficient approach for simulating nonadiabatic molecular dynamics (NA-MD) of large systems in the framework of the self-consistent charge density functional tight binding (SCC-DFTB) method. SCC-DFTB is combined with the fewest switches surface hopping (FSSH) and decoherence induced surface hopping (DISH) techniques for NA-MD. The approach is implemented within the Python extension for the ab initio dynamics (PYXAID) simulation package, which is an open source NA-MD program designed to handle nanoscale materials. The accuracy of the developed approach is tested with ab initio DFT and experimental data, by considering intraband electron and hole relaxation, and nonradiative electron-hole recombination in a CdSe quantum dot and the (10,5) semiconducting carbon nanotube. The technique is capable of treating accurately and efficiently excitation dynamics in large, realistic nanoscale materials, employing modest computational resources.
NASA's Solar Dynamics Observatory (SDO): A Systems Approach to a Complex Mission
NASA Technical Reports Server (NTRS)
Ruffa, John A.; Ward, David K.; Bartusek, LIsa M.; Bay, Michael; Gonzales, Peter J.; Pesnell, William D.
2012-01-01
The Solar Dynamics Observatory (SDO) includes three advanced instruments, massive science data volume, stringent science data completeness requirements, and a custom ground station to meet mission demands. The strict instrument science requirements imposed a number of challenging drivers on the overall mission system design, leading the SDO team to adopt an integrated systems engineering presence across all aspects of the mission to ensure that mission science requirements would be met. Key strategies were devised to address these system level drivers and mitigate identified threats to mission success. The global systems engineering team approach ensured that key drivers and risk areas were rigorously addressed through all phases of the mission, leading to the successful SDO launch and on-orbit operation. Since launch, SDO's on-orbit performance has met all mission science requirements and enabled groundbreaking science observations, expanding our understanding of the Sun and its dynamic processes.
NASA's Solar Dynamics Observatory (SDO): A Systems Approach to a Complex Mission
NASA Technical Reports Server (NTRS)
Ruffa, John A.; Ward, David K.; Bartusek, Lisa M.; Bay, Michael; Gonzales, Peter J.; Pesnell, William D.
2012-01-01
The Solar Dynamics Observatory (SDO) includes three advanced instruments, massive science data volume, stringent science data completeness requirements, and a custom ground station to meet mission demands. The strict instrument science requirements imposed a number of challenging drivers on the overall mission system design, leading the SDO team to adopt an integrated systems engineering presence across all aspects of the mission to ensure that mission science requirements would be met. Key strategies were devised to address these system level drivers and mitigate identified threats to mission success. The global systems engineering team approach ensured that key drivers and risk areas were rigorously addressed through all phases of the mission, leading to the successful SDO launch and on-orbit operation. Since launch, SDO s on-orbit performance has met all mission science requirements and enabled groundbreaking science observations, expanding our understanding of the Sun and its dynamic processes.
NASA Astrophysics Data System (ADS)
Ma, Zhisai; Liu, Li; Zhou, Sida; Naets, Frank; Heylen, Ward; Desmet, Wim
2017-03-01
The problem of linear time-varying(LTV) system modal analysis is considered based on time-dependent state space representations, as classical modal analysis of linear time-invariant systems and current LTV system modal analysis under the "frozen-time" assumption are not able to determine the dynamic stability of LTV systems. Time-dependent state space representations of LTV systems are first introduced, and the corresponding modal analysis theories are subsequently presented via a stability-preserving state transformation. The time-varying modes of LTV systems are extended in terms of uniqueness, and are further interpreted to determine the system's stability. An extended modal identification is proposed to estimate the time-varying modes, consisting of the estimation of the state transition matrix via a subspace-based method and the extraction of the time-varying modes by the QR decomposition. The proposed approach is numerically validated by three numerical cases, and is experimentally validated by a coupled moving-mass simply supported beam experimental case. The proposed approach is capable of accurately estimating the time-varying modes, and provides a new way to determine the dynamic stability of LTV systems by using the estimated time-varying modes.
Combined analytical and numerical approaches in Dynamic Stability analyses of engineering systems
NASA Astrophysics Data System (ADS)
Náprstek, Jiří
2015-03-01
Dynamic Stability is a widely studied area that has attracted many researchers from various disciplines. Although Dynamic Stability is usually associated with mechanics, theoretical physics or other natural and technical disciplines, it is also relevant to social, economic, and philosophical areas of our lives. Therefore, it is useful to occasionally highlight the general aspects of this amazing area, to present some relevant examples and to evaluate its position among the various branches of Rational Mechanics. From this perspective, the aim of this study is to present a brief review concerning the Dynamic Stability problem, its basic definitions and principles, important phenomena, research motivations and applications in engineering. The relationships with relevant systems that are prone to stability loss (encountered in other areas such as physics, other natural sciences and engineering) are also noted. The theoretical background, which is applicable to many disciplines, is presented. In this paper, the most frequently used Dynamic Stability analysis methods are presented in relation to individual dynamic systems that are widely discussed in various engineering branches. In particular, the Lyapunov function and exponent procedures, Routh-Hurwitz, Liénard, and other theorems are outlined together with demonstrations. The possibilities for analytical and numerical procedures are mentioned together with possible feedback from experimental research and testing. The strengths and shortcomings of these approaches are evaluated together with examples of their effective complementing of each other. The systems that are widely encountered in engineering are presented in the form of mathematical models. The analyses of their Dynamic Stability and post-critical behaviour are also presented. The stability limits, bifurcation points, quasi-periodic response processes and chaotic regimes are discussed. The limit cycle existence and stability are examined together with their
NASA Astrophysics Data System (ADS)
Feng, Maoyuan; Liu, Pan; Li, Zejun; Zhang, Jingwen; Liu, Dedi; Xiong, Lihua
2016-12-01
Nexus approaches address the complex interconnections across coupled systems, providing a new and effective way to identify the dynamics of coevolution process. The connections across water supply, power generation and environment (WPE) systems are increasingly tight and thus can be profiled as a WPE nexus. This paper aims to model the WPE nexus in the China's Hehuang Region by using the system dynamics approach. Six nonlinear ordinary differential equations of storage, water supply, power generation, population, biomass, and environmental awareness are formulated to dominate the coevolution process. Their constitutive relations are then obtained from observed data to complete the WPE nexus model. The results show that the system dynamics approach is competent in modeling the WPE nexus of the Hehuang Region. The coevolution process is divided into four cyclic stages (i.e., exploitation, deterioration, depression and recovery stages) and terminates with a stationary cycling after thousands of years. The dynamics of state variables are explicitly interpreted to show how different driving variables affect the variations of system states. The observations obtained by modeling the nexus are insightful, improving the understanding of interactions across coupled systems.
Melt Segregation in Crustal Magmatic Systems: A Coupled Dynamics and Thermodynamics Approach
NASA Astrophysics Data System (ADS)
Dufek, J.; Ghiorso, M. S.
2011-12-01
Compositional diversity in evolving magmatic systems is driven in large part by the multiphase dynamics of melt-crystal separation. Key to quantitative description of these systems is to accurately calculate the rate and timing of crystal-melt separation. This calculation involves three separate, but closely linked, problems: heat transfer, phase equilibria, and multiphase dynamics. To examine these problems we have developed a coupled fluid dynamics and thermodynamics approach. With this approach we can determine the spatial and temporal variability in composition, melt fraction, phase equilibrium, and velocities of different crystal phases and melt. We use a multiphase (Eulerian-Eulerian-Lagrangian, EEL) approach to compute extraction in magmatic systems (Dufek and Bachmann, 2010). Each phase (melt or crystal phase) is represented by conservation equations for the mass, momentum and enthalpy. Enthalpy closure is determined from a version of rhyolite-MELTS with callable library functions that provide phase equilibrium results to the fluid dynamics code (Ghiorso and Sack, 1995; Gualda et al, 2011). This method accounts for the partitioning of latent and sensible heat in complex geochemical systems. Further, phase properties (for example density and heat capacity) are determined using MELTS, and as such are internally consistent with extensive thermodynamic and experimental data. Chemical species for each phase (major oxides) have separate transport equations permitting the exploration of fractionation behavior as well as providing detailed geochemical information that can be used to compare to field observations (e.g. solid solution in phases, major oxide composition of melts). A typical simulation involves millions of phase equilibrium calculations and transport of several crystalline phases. We have parallelized this approach to work on large cluster computers for extensive calculations, and are working toward a publically available version. We use this new model
Minimax terminal approach problem in two-level hierarchical nonlinear discrete-time dynamical system
Shorikov, A. F.
2015-11-30
We consider a discrete–time dynamical system consisting of three controllable objects. The motions of all objects are given by the corresponding vector nonlinear or linear discrete–time recurrent vector relations, and control system for its has two levels: basic (first or I level) that is dominating and subordinate level (second or II level) and both have different criterions of functioning and united a priori by determined informational and control connections defined in advance. For the dynamical system in question, we propose a mathematical formalization in the form of solving a multistep problem of two-level hierarchical minimax program control over the terminal approach process with incomplete information and give a general scheme for its solving.
A Dynamical Systems Approach to Understanding Self-Regulation in Smoking Cessation Behavior Change
2014-01-01
Introduction: Self-regulation, a key component of the addiction process, has been challenging to model precisely in smoking cessation settings, largely due to the limitations of traditional methodological approaches in measuring behavior over time. However, increased availability of intensive longitudinal data (ILD) measured through ecological momentary assessment facilitates the novel use of an engineering modeling approach to better understand self-regulation. Methods: Dynamical systems modeling is a mature engineering methodology that can represent smoking cessation as a self-regulation process. This article shows how a dynamical systems approach effectively captures the reciprocal relationship between day-to-day changes in craving and smoking. Models are estimated using ILD from a smoking cessation randomized clinical trial. Results: A system of low-order differential equations is presented that models cessation as a self-regulatory process. It explains 87.32% and 89.16% of the variance observed in craving and smoking levels, respectively, for an active treatment group and 62.25% and 84.12% of the variance in a control group. The models quantify the initial increase and subsequent gradual decrease in craving occurring postquit as well as the dramatic quit-induced smoking reduction and postquit smoking resumption observed in both groups. Comparing the estimated parameters for the group models suggests that active treatment facilitates craving reduction and slows postquit smoking resumption. Conclusions: This article illustrates that dynamical systems modeling can effectively leverage ILD in order to understand self-regulation within smoking cessation. Such models quantify group-level dynamic responses in smoking cessation and can inform the development of more effective interventions in the future. PMID:24064386
Saturated Nussbaum Function Based Approach for Robotic Systems With Unknown Actuator Dynamics.
Chen, Ci; Liu, Zhi; Zhang, Yun; Chen, C L Philip; Xie, Shengli
2016-10-01
This paper presents a saturated Nussbaum function based approach for robotic systems with unknown actuator dynamics. To eliminate the effect of the control shock from the traditional Nussbaum function, a new type of the saturated Nussbaum function is developed with the idea of time-elongation. Moreover, by exploiting properties of the proposed Nussbaum function, a promising theorem is established to deal with unknown multiple actuator nonlinearities. In what follows, the proposed theorem is integrated with the adaptive control technique such that the stability analysis of the robotic system is completed. It thus guarantees that the state of the robotic system asymptotically converges to the desired trajectory. Finally, comparative studies are carried out to validate the effectiveness and the superiority of the proposed approach.
Constrained molecular dynamics II: An N-body approach to nuclear systems
Papa, M. . E-mail: massimo.papa@ct.infn.it; Giuliani, G.; Bonasera, A.
2005-09-20
In this work, we illustrate the basic development of the constrained molecular dynamics applied to the N-body problem in nuclear physics. The heavy computational tasks related to quantum effects, to the Fermionic nature of the system have been resolved out by defining a set of transformations based on the concept of impulsive forces. In particular, in the implemented version II of the constrained molecular dynamics model the problem related to the non-conservation of the total angular momentum has been solved. This problem affects other semi-classical microscopic approaches due to the 'hard core' repulsive interaction and, more generally, to the usage of random forces. The effect of the restored conservation law on the fusion cross-section for the {sup 40}Ca + {sup 40}Ca system is also briefly discussed.
A System Dynamics Approach to the Efficacy of Oxime Therapy in Sub Lethal Exposure to Sarin Gas
2015-06-18
distribution through the circulatory system . Symptoms typically peak within 15 to 30 minutes after exposure (Cannard, 2006:89). 15 Antidote...A SYSTEM DYNAMICS APPROACH TO THE EFFICACY OF OXIME THERAPY IN SUB LETHAL EXPOSURE TO SARIN GAS...subject to copyright protection in the United States. iii AFIT-ENV-15-J-053 A SYSTEM DYNAMICS APPROACH TO THE EFFICACY OF OXIME THERAPY
Information-driven self-organization: the dynamical system approach to autonomous robot behavior.
Ay, Nihat; Bernigau, Holger; Der, Ralf; Prokopenko, Mikhail
2012-09-01
In recent years, information theory has come into the focus of researchers interested in the sensorimotor dynamics of both robots and living beings. One root for these approaches is the idea that living beings are information processing systems and that the optimization of these processes should be an evolutionary advantage. Apart from these more fundamental questions, there is much interest recently in the question how a robot can be equipped with an internal drive for innovation or curiosity that may serve as a drive for an open-ended, self-determined development of the robot. The success of these approaches depends essentially on the choice of a convenient measure for the information. This article studies in some detail the use of the predictive information (PI), also called excess entropy or effective measure complexity, of the sensorimotor process. The PI of a process quantifies the total information of past experience that can be used for predicting future events. However, the application of information theoretic measures in robotics mostly is restricted to the case of a finite, discrete state-action space. This article aims at applying the PI in the dynamical systems approach to robot control. We study linear systems as a first step and derive exact results for the PI together with explicit learning rules for the parameters of the controller. Interestingly, these learning rules are of Hebbian nature and local in the sense that the synaptic update is given by the product of activities available directly at the pertinent synaptic ports. The general findings are exemplified by a number of case studies. In particular, in a two-dimensional system, designed at mimicking embodied systems with latent oscillatory locomotion patterns, it is shown that maximizing the PI means to recognize and amplify the latent modes of the robotic system. This and many other examples show that the learning rules derived from the maximum PI principle are a versatile tool for the self
Nie, Xianghui; Huang, Guo H; Li, Yongping
2009-11-01
This study integrates the concepts of interval numbers and fuzzy sets into optimization analysis by dynamic programming as a means of accounting for system uncertainty. The developed interval fuzzy robust dynamic programming (IFRDP) model improves upon previous interval dynamic programming methods. It allows highly uncertain information to be effectively communicated into the optimization process through introducing the concept of fuzzy boundary interval and providing an interval-parameter fuzzy robust programming method for an embedded linear programming problem. Consequently, robustness of the optimization process and solution can be enhanced. The modeling approach is applied to a hypothetical problem for the planning of waste-flow allocation and treatment/disposal facility expansion within a municipal solid waste (MSW) management system. Interval solutions for capacity expansion of waste management facilities and relevant waste-flow allocation are generated and interpreted to provide useful decision alternatives. The results indicate that robust and useful solutions can be obtained, and the proposed IFRDP approach is applicable to practical problems that are associated with highly complex and uncertain information.
Freebairn, Louise; Rychetnik, Lucie; Atkinson, Jo-An; Kelly, Paul; McDonnell, Geoff; Roberts, Nick; Whittall, Christine; Redman, Sally
2017-10-02
Evidence-based decision-making is an important foundation for health policy and service planning decisions, yet there remain challenges in ensuring that the many forms of available evidence are considered when decisions are being made. Mobilising knowledge for policy and practice is an emergent process, and one that is highly relational, often messy and profoundly context dependent. Systems approaches, such as dynamic simulation modelling can be used to examine both complex health issues and the context in which they are embedded, and to develop decision support tools. This paper reports on the novel use of participatory simulation modelling as a knowledge mobilisation tool in Australian real-world policy settings. We describe how this approach combined systems science methodology and some of the core elements of knowledge mobilisation best practice. We describe the strategies adopted in three case studies to address both technical and socio-political issues, and compile the experiential lessons derived. Finally, we consider the implications of these knowledge mobilisation case studies and provide evidence for the feasibility of this approach in policy development settings. Participatory dynamic simulation modelling builds on contemporary knowledge mobilisation approaches for health stakeholders to collaborate and explore policy and health service scenarios for priority public health topics. The participatory methods place the decision-maker at the centre of the process and embed deliberative methods and co-production of knowledge. The simulation models function as health policy and programme dynamic decision support tools that integrate diverse forms of evidence, including research evidence, expert knowledge and localised contextual information. Further research is underway to determine the impact of these methods on health service decision-making.
A Bayesian Approach for Parameter Estimation with Uncertainty for Dynamic Power Systems
Petra, Noemi; Petra, Cosmin G.; Zhang, Zheng; ...
2017-07-01
We address the problem of estimating the uncertainty in the solution of power grid inverse problems within the framework of Bayesian inference. We investigate two approaches, an adjoint-based method and a stochastic spectral method. These methods are used to estimate the maximum a posteriori point of the parameters and their variance, which quantifies their uncertainty. Within this framework, we estimate several parameters of the dynamic power system, such as generator inertias, which are not quantifiable in steady- state models. We illustrate the performance of these approaches on a 9-bus power grid example and analyze the dependence on measurement frequency, estimationmore » horizon, perturbation size, andmeasurement noise. We assess the computational efficiency, and discuss the expected performance when these methods are applied to large systems.« less
A new approach for the characterization of reverse micellar systems by dynamic light scattering.
Lemyre, Jean-Luc; Lamarre, Sébastien; Beaupré, Ariane; Ritcey, Anna M
2010-07-06
This paper reports the use of dynamic light scattering (DLS) to study reverse micelles formed by the water/Igepal CO-520/cyclohexane system over a large range of global compositions. A novel approach for data analysis is presented, based on the realization that micelles of a given size must be in equilibrium with free surfactant of a fixed concentration. Compilation of the DLS data into sets of fixed micelle size but differing global compositions therefore allows for the determination of parameters such as free surfactant concentration, micellar molar composition, surfactant interfacial area, and aggregation numbers. Importantly, this method gives access to the variation of each of these parameters with micelle size, as is essential for the characterization of reverse micelles formed by nonionic surfactants. This approach constitutes a significant complement to other available characterization methods. The analysis also provides insight into the primary factors controlling the equilibrium distribution of surfactant within the system and the relative stability of the micelles.
A knowledge-based approach to identification and adaptation in dynamical systems control
NASA Technical Reports Server (NTRS)
Glass, B. J.; Wong, C. M.
1988-01-01
Artificial intelligence techniques are applied to the problems of model form and parameter identification of large-scale dynamic systems. The object-oriented knowledge representation is discussed in the context of causal modeling and qualitative reasoning. Structured sets of rules are used for implementing qualitative component simulations, for catching qualitative discrepancies and quantitative bound violations, and for making reconfiguration and control decisions that affect the physical system. These decisions are executed by backward-chaining through a knowledge base of control action tasks. This approach was implemented for two examples: a triple quadrupole mass spectrometer and a two-phase thermal testbed. Results of tests with both of these systems demonstrate that the software replicates some or most of the functionality of a human operator, thereby reducing the need for a human-in-the-loop in the lower levels of control of these complex systems.
Ishikawa, Tomoki; Ohba, Hisateru; Yokooka, Yuki; Nakamura, Kozo; Ogasawara, Katsuhiko
2013-08-27
In Japan, a shortage of physicians, who serve a key role in healthcare provision, has been pointed out as a major medical issue. The healthcare workforce policy planner should consider future dynamic changes in physician numbers. The purpose of this study was to propose a physician supply forecasting methodology by applying system dynamics modeling to estimate future absolute and relative numbers of physicians. We constructed a forecasting model using a system dynamics approach. Forecasting the number of physician was performed for all clinical physician and OB/GYN specialists. Moreover, we conducted evaluation of sufficiency for the number of physicians and sensitivity analysis. As a result, it was forecast that the number of physicians would increase during 2008-2030 and the shortage would resolve at 2026 for all clinical physicians. However, the shortage would not resolve for the period covered. This suggests a need for measures for reconsidering the allocation system of new entry physicians to resolve maldistribution between medical departments, in addition, for increasing the overall number of clinical physicians.
NASA Astrophysics Data System (ADS)
Fazanaro, Filipe I.; Soriano, Diogo C.; Suyama, Ricardo; Madrid, Marconi K.; Oliveira, José Raimundo de; Muñoz, Ignacio Bravo; Attux, Romis
2016-08-01
The characterization of nonlinear dynamical systems and their attractors in terms of invariant measures, basins of attractions and the structure of their vector fields usually outlines a task strongly related to the underlying computational cost. In this work, the practical aspects related to the use of parallel computing - specially the use of Graphics Processing Units (GPUS) and of the Compute Unified Device Architecture (CUDA) - are reviewed and discussed in the context of nonlinear dynamical systems characterization. In this work such characterization is performed by obtaining both local and global Lyapunov exponents for the classical forced Duffing oscillator. The local divergence measure was employed by the computation of the Lagrangian Coherent Structures (LCSS), revealing the general organization of the flow according to the obtained separatrices, while the global Lyapunov exponents were used to characterize the attractors obtained under one or more bifurcation parameters. These simulation sets also illustrate the required computation time and speedup gains provided by different parallel computing strategies, justifying the employment and the relevance of GPUS and CUDA in such extensive numerical approach. Finally, more than simply providing an overview supported by a representative set of simulations, this work also aims to be a unified introduction to the use of the mentioned parallel computing tools in the context of nonlinear dynamical systems, providing codes and examples to be executed in MATLAB and using the CUDA environment, something that is usually fragmented in different scientific communities and restricted to specialists on parallel computing strategies.
A compartmental-spatial system dynamics approach to ground water modeling.
Roach, Jesse; Tidwell, Vince
2009-01-01
High-resolution, spatially distributed ground water flow models can prove unsuitable for the rapid, interactive analysis that is increasingly demanded to support a participatory decision environment. To address this shortcoming, we extend the idea of multiple cell (Bear 1979) and compartmental (Campana and Simpson 1984) ground water models developed within the context of spatial system dynamics (Ahmad and Simonovic 2004) for rapid scenario analysis. We term this approach compartmental-spatial system dynamics (CSSD). The goal is to balance spatial aggregation necessary to achieve a real-time integrative and interactive decision environment while maintaining sufficient model complexity to yield a meaningful representation of the regional ground water system. As a test case, a 51-compartment CSSD model was built and calibrated from a 100,0001 cell MODFLOW (McDonald and Harbaugh 1988) model of the Albuquerque Basin in central New Mexico (McAda and Barroll 2002). Seventy-seven percent of historical drawdowns predicted by the MODFLOW model were within 1 m of the corresponding CSSD estimates, and in 80% of the historical model run years the CSSD model estimates of river leakage, reservoir leakage, ground water flow to agricultural drains, and riparian evapotranspiration were within 30% of the corresponding estimates from McAda and Barroll (2002), with improved model agreement during the scenario period. Comparisons of model results demonstrate both advantages and limitations of the CCSD model approach.
Barthès, Jennifer; Bulone, Donatella; Manno, Mauro; Martorana, Vincenzo; San Biagio, Pier Luigi
2007-09-01
Light scattering is a powerful technique to study the structural and dynamical properties of biomolecular systems or other soft materials such as polymeric solutions and blends or gels. An important application of this technique is the study of the kinetics of formation of supramolecular structures. However, in such cases, the system under study is rapidly changing, and consequently the integration time for each measurement is limited. In order to overcome this difficulty, a statistical approach has been developed based on the analysis of the scattered light intensity distribution (Manno et al. 2006, 2004). Indeed the intensity distribution depends upon the ratio between the integration time of each measurement and the coherence time of scattered radiation. This method has been applied to protein aggregation (Manno et al. 2006) and to sol-gel transition (Manno et al. 2004), to obtain information on the heterogeneity of morphological and dynamical features during such processes. In the present work, we accurately test the validity of this approach by analyzing the statistical properties of the light scattered by a model system: a solution of polystyrene spherical macromolecules of different sizes. Each molecular size is related to a given diffusion coefficient and to a given coherence time of the scattered intensity. The effect of changing the experimental integration time is systematically investigated. A mixture of particles of two different sizes is also analyzed to test the validity and robustness of the model based on the convolution of a gaussian with an exponential distribution.
A dynamical systems approach to the tilted Bianchi models of solvable type
NASA Astrophysics Data System (ADS)
Coley, Alan; Hervik, Sigbjørn
2005-02-01
We use a dynamical systems approach to analyse the tilting spatially homogeneous Bianchi models of solvable type (e.g., types VIh and VIIh) with a perfect fluid and a linear barotropic γ-law equation of state. In particular, we study the late-time behaviour of tilted Bianchi models, with an emphasis on the existence of equilibrium points and their stability properties. We briefly discuss the tilting Bianchi type V models and the late-time asymptotic behaviour of irrotational Bianchi type VII0 models. We prove the important result that for non-inflationary Bianchi type VIIh models vacuum plane-wave solutions are the only future attracting equilibrium points in the Bianchi type VIIh invariant set. We then investigate the dynamics close to the plane-wave solutions in more detail, and discover some new features that arise in the dynamical behaviour of Bianchi cosmologies with the inclusion of tilt. We point out that in a tiny open set of parameter space in the type IV model (the loophole) there exist closed curves which act as attracting limit cycles. More interestingly, in the Bianchi type VIIh models there is a bifurcation in which a set of equilibrium points turns into closed orbits. There is a region in which both sets of closed curves coexist, and it appears that for the type VIIh models in this region the solution curves approach a compact surface which is topologically a torus.
Dynamic systems approaches and levels of analysis in the nervous system
Parker, David; Srivastava, Vipin
2013-01-01
Various analyses are applied to physiological signals. While epistemological diversity is necessary to address effects at different levels, there is often a sense of competition between analyses rather than integration. This is evidenced by the differences in the criteria needed to claim understanding in different approaches. In the nervous system, neuronal analyses that attempt to explain network outputs in cellular and synaptic terms are rightly criticized as being insufficient to explain global effects, emergent or otherwise, while higher-level statistical and mathematical analyses can provide quantitative descriptions of outputs but can only hypothesize on their underlying mechanisms. The major gap in neuroscience is arguably our inability to translate what should be seen as complementary effects between levels. We thus ultimately need approaches that allow us to bridge between different spatial and temporal levels. Analytical approaches derived from critical phenomena in the physical sciences are increasingly being applied to physiological systems, including the nervous system, and claim to provide novel insight into physiological mechanisms and opportunities for their control. Analyses of criticality have suggested several important insights that should be considered in cellular analyses. However, there is a mismatch between lower-level neurophysiological approaches and statistical phenomenological analyses that assume that lower-level effects can be abstracted away, which means that these effects are unknown or inaccessible to experimentalists. As a result experimental designs often generate data that is insufficient for analyses of criticality. This review considers the relevance of insights from analyses of criticality to neuronal network analyses, and highlights that to move the analyses forward and close the gap between the theoretical and neurobiological levels, it is necessary to consider that effects at each level are complementary rather than in
A hybrid approach for modelling dynamic behaviours of a rotor-foundation system
NASA Astrophysics Data System (ADS)
Zhang, Z. G.; Zhang, Z. Y.; Jing, B.; Hua, H. X.
2016-09-01
A new hybrid approach is presented to study the dynamic behaviour of a rotor- foundation system, in which a shaft coupled with various discontinuities are connected to a flexible foundation via discrete spring subunits. By modelling the rotor with the modified transfer matrix method and describing the flexible foundation through the appropriate modal model, the proposed technique facilitates a computationally efficient modelling approach where a mixture of theoretical, numerical or experimental models can be incorporated into one overall numerical model. Particularly, the present model enables one to conveniently consider both the free and forced vibrations as well as effects of various combinations of discontinuities encountered in the rotor. Some results are compared with available results in previous publications and those from the finite element method to validate the model. Parametric studies are also performed to demonstrate the accuracy and versatility of the developed method for substructure coupling analysis.
NASA Astrophysics Data System (ADS)
Andia, Pedro C.
The topic of this dissertation is the study of the mechanical properties of solid material systems at the nanoscale. At such length scales, materials can be viewed as particle systems, and molecular dynamics (MD) simulations help one understand their behavior as well as quantify their properties. However, mechanical concepts such as strain, stress and moduli were originally developed in continuum models, which are typically applied in space scales that range from the microscopic to the macroscopic. For this reason, a careful translation of ideas from continuum scales to the nanoscale is necessary. In essence, this thesis reviews and refines the continuum notions of average mechanical properties, such as stress and strain, and the meaning of such notions when MD is used to compute them. A Lagrangian-based approach is utilized for the purpose of determining the stress-deformation behavior of continua as well as of particle systems. At the continuum level, the mentioned Lagrangian-based approach is applied within homogenization theory for developing a nonlinear continuum homogenization model, which includes a novel constitutive relation for the stress. At the nanoscale, an MD method is presented as the extension of the continuum homogenization model. This MD method is able to simulate the behavior of particle systems under a given type of deformation as well as to generate stress-strain curves. In the process of developing the MD method, some concepts and techniques commonly used in MD, such as the virial stress and the Parrinello-Rahman method, are clarified.
Patterns of Horse-Rider Coordination during Endurance Race: A Dynamical System Approach
Viry, Sylvain; Sleimen-Malkoun, Rita; Temprado, Jean-Jacques; Frances, Jean-Philippe; Berton, Eric; Laurent, Michel; Nicol, Caroline
2013-01-01
In riding, most biomechanical studies have focused on the description of the horse locomotion in unridden condition. In this study, we draw the prospect of how the basic principles established in inter-personal coordination by the theory of Coordination Dynamics may provide a conceptual and methodological framework for understanding the horse-rider coupling. The recent development of mobile technologies allows combined horse and rider recordings during long lasting natural events such as endurance races. Six international horse-rider dyads were thus recorded during a 120 km race by using two tri-axial accelerometers placed on the horses and riders, respectively. The analysis concentrated on their combined vertical displacements. The obtained shapes and angles of Lissajous plots together with values of relative phase between horse and rider displacements at lower reversal point allowed us to characterize four coordination patterns, reflecting the use of two riding techniques per horse's gait (trot and canter). The present study shows that the concepts, methods and tools of self-organizing dynamic system approach offer new directions for understanding horse-rider coordination. The identification of the horse-rider coupling patterns constitutes a firm basis to further study the coalition of multiple constraints that determine their emergence and their dynamics in endurance race. PMID:23940788
Patterns of horse-rider coordination during endurance race: a dynamical system approach.
Viry, Sylvain; Sleimen-Malkoun, Rita; Temprado, Jean-Jacques; Frances, Jean-Philippe; Berton, Eric; Laurent, Michel; Nicol, Caroline
2013-01-01
In riding, most biomechanical studies have focused on the description of the horse locomotion in unridden condition. In this study, we draw the prospect of how the basic principles established in inter-personal coordination by the theory of Coordination Dynamics may provide a conceptual and methodological framework for understanding the horse-rider coupling. The recent development of mobile technologies allows combined horse and rider recordings during long lasting natural events such as endurance races. Six international horse-rider dyads were thus recorded during a 120 km race by using two tri-axial accelerometers placed on the horses and riders, respectively. The analysis concentrated on their combined vertical displacements. The obtained shapes and angles of Lissajous plots together with values of relative phase between horse and rider displacements at lower reversal point allowed us to characterize four coordination patterns, reflecting the use of two riding techniques per horse's gait (trot and canter). The present study shows that the concepts, methods and tools of self-organizing dynamic system approach offer new directions for understanding horse-rider coordination. The identification of the horse-rider coupling patterns constitutes a firm basis to further study the coalition of multiple constraints that determine their emergence and their dynamics in endurance race.
Robust controller designs for second-order dynamic system: A virtual passive approach
NASA Technical Reports Server (NTRS)
Juang, Jer-Nan; Phan, Minh
1990-01-01
A robust controller design is presented for second-order dynamic systems. The controller is model-independent and itself is a virtual second-order dynamic system. Conditions on actuator and sensor placements are identified for controller designs that guarantee overall closed-loop stability. The dynamic controller can be viewed as a virtual passive damping system that serves to stabilize the actual dynamic system. The control gains are interpreted as virtual mass, spring, and dashpot elements that play the same roles as actual physical elements in stability analysis. Position, velocity, and acceleration feedback are considered. Simple examples are provided to illustrate the physical meaning of this controller design.
A system dynamics approach for integrated management of the Jucar River Basin
NASA Astrophysics Data System (ADS)
Rubio-Martin, Adria; Macian-Sorribes, Hector; Pulido-Velazquez, Manuel
2017-04-01
System dynamics (SD) is a modelling approach that allows the analysis of complex systems through the mathematical definition of variables and their relationships. Based on systems thinking, SD is suitable for interdisciplinary studies of the management of complex systems. Over the past 50 years, SD tools have been applied to fields as diverse as economics, ecology, politics, sociology and resource management. Its application to the field of water resources has grown significantly over the last two decades, facilitating the enhancement of models by adding social, economic and ecological components. However, its application to the operation of complex multireservoir systems has been very limited so far. In this contribution, we have developed a SD model for the Jucar River Basin, one of the most vulnerable basins in the western Mediterranean region with regard to droughts. The system has three main reservoirs, which allows for a multiannual management of the storage that compensates the highly variable streamflow from upstream. Our SD model of the Jucar River Basin is able to capture the complexity of the water resource system. The model developed consists of five interlinked subsystems: a) Topology of the system network, including the 3 main reservoirs, water seepage and evaporation, inflows and catchments. b) Monthly operating rules of each reservoir. The rules were derived from the expert knowledge eluded from the operators of the reservoirs. c) Monthly urban, agricultural and environmental water demands. d) State index of the system and drought mitigation measures triggered depending on the state index. e) Mancha Oriental aquifer and stream-aquifer interaction with the Jucar River. The comparison between observed and simulated series showed that the model provides a good representation of the observed reservoir operation and total deficits. The interdisciplinary and open nature of the methodology allows to add new variables and dynamics to the model that are
Dynamical systems approach to the study of a sociophysics agent-based model
Timpanaro, Andre M.; Prado, Carmen P. C.
2011-03-24
The Sznajd model is a Potts-like model that has been studied in the context of sociophysics [1,2](where spins are interpreted as opinions). In a recent work [3], we generalized the Sznajd model to include assymetric interactions between the spins (interpreted as biases towards opinions) and used dynamical systems techniques to tackle its mean-field version, given by the flow: {eta}{sub {sigma}} = {Sigma}{sub {sigma}}'{sup M} = 1{eta}{sub {sigma}}{eta}{sigma}'({eta}{sub {sigma}}{rho}{sigma}'{yields}{sigma}-{sigma}'{rho}{sigma}{yields}{sigma}').Where hs is the proportion of agents with opinion (spin){sigma}', M is the number of opinions and {sigma}'{yields}{sigma}' is the probability weight for an agent with opinion {sigma} being convinced by another agent with opinion {sigma}'. We made Monte Carlo simulations of the model in a complex network (using Barabasi-Albert networks [4]) and they displayed the same attractors than the mean-field. Using linear stability analysis, we were able to determine the mean-field attractor structure analytically and to show that it has connections with well known graph theory problems (maximal independent sets and positive fluxes in directed graphs). Our dynamical systems approach is quite simple and can be used also in other models, like the voter model.
A nonlinear dynamical system approach for the yielding behaviour of a viscoplastic material.
Burghelea, Teodor; Moyers-Gonzalez, Miguel; Sainudiin, Raazesh
2017-02-15
A nonlinear dynamical system model that approximates a microscopic Gibbs field model for the yielding of a viscoplastic material subjected to varying external stresses recently reported in R. Sainudiin, M. Moyers-Gonzalez and T. Burghelea, Soft Matter, 2015, 11(27), 5531-5545 is presented. The predictions of the model are in fair agreement with microscopic simulations and are in very good agreement with the micro-structural semi-empirical model reported in A. M. V. Putz and T. I. Burghelea, Rheol. Acta, 2009, 48, 673-689. With only two internal parameters, the nonlinear dynamical system model captures several key features of the solid-fluid transition observed in experiments: the effect of the interactions between microscopic constituents on the yield point, the abruptness of solid-fluid transition and the emergence of a hysteresis of the micro-structural states upon increasing/decreasing external forces. The scaling behaviour of the magnitude of the hysteresis with the degree of the steadiness of the flow is consistent with previous experimental observations. Finally, the practical usefulness of the approach is demonstrated by fitting a rheological data set measured with an elasto-viscoplastic material.
Dynamical systems approach to the study of a sociophysics agent-based model
NASA Astrophysics Data System (ADS)
Timpanaro, André M.; Prado, Carmen P. C.
2011-03-01
The Sznajd model is a Potts-like model that has been studied in the context of sociophysics [1,2] (where spins are interpreted as opinions). In a recent work [3], we generalized the Sznajd model to include assymetric interactions between the spins (interpreted as biases towards opinions) and used dynamical systems techniques to tackle its mean-field version, given by the flow: ησ = ∑ σ' = 1Mησησ'(ησρσ'→σ-σ'ρσ→σ'). Where hs is the proportion of agents with opinion (spin) σ', M is the number of opinions and σ'→σ' is the probability weight for an agent with opinion σ being convinced by another agent with opinion σ'. We made Monte Carlo simulations of the model in a complex network (using Barabási-Albert networks [4]) and they displayed the same attractors than the mean-field. Using linear stability analysis, we were able to determine the mean-field attractor structure analytically and to show that it has connections with well known graph theory problems (maximal independent sets and positive fluxes in directed graphs). Our dynamical systems approach is quite simple and can be used also in other models, like the voter model.
Stream restoration in dynamic fluvial systems: Scientific approaches, analyses, and tools
NASA Astrophysics Data System (ADS)
Schultz, Colin
2012-04-01
In the United States the average annual investment in river restoration programs is approximately $1 billion. Despite this burgeoning industry, the National Water Quality Inventory, which tracks the health of the nation's rivers, has shown no serious improvement in cumulative river health since the early 1990s. In the AGU monographStream Restoration in Dynamic Fluvial Systems: Scientific Approaches, Analyses, and Tools, editors Andrew Simon, Sean J. Bennett, and Janine M. Castro pull together the latest evidence-based understanding of stream restoration practices, with an aim of guiding the further development of the field and helping to right its apparently unsuccessful course. In this interview, Eos talks to Sean J. Bennett, University of Buffalo, about the culture, practice, and promise of restoring rivers.
Leitão, Selma
2008-06-01
The focus of this commentary is twofold. First, I examine Faiciuc's attempts to counter symbolic computationalism as a major theoretical framework for the study of deductive reasoning. Second, I wish to see how far the author goes in her defense of Dynamic Systems Approaches (DSAs) as a more promising framework for explaining logical reasoning. When reading her work, I posed two versions of the same for/against question to myself: How strong is the case against symbolic computationalism? And, on the basis of the author's argumentation, would one feel justified in adopting DSAs instead? I examine each question in turn, and come to similar conclusions. The article by Faiciuc tackles issues of relevance to any serious effort toward reflecting on the two perspectives being compared. Unfortunately, however, references to studies supporting her claims are rather thin. A better-informed answer to the question raised in the title of the article is still to be given.
Demand forecasting for automotive sector in Malaysia by system dynamics approach
Zulkepli, Jafri Abidin, Norhaslinda Zainal; Fong, Chan Hwa
2015-12-11
In general, Proton as an automotive company needs to forecast future demand of the car to assist in decision making related to capacity expansion planning. One of the forecasting approaches that based on judgemental or subjective factors is normally used to forecast the demand. As a result, demand could be overstock that eventually will increase the operation cost; or the company will face understock, which resulted losing their customers. Due to automotive industry is very challenging process because of high level of complexity and uncertainty involved in the system, an accurate tool to forecast the future of automotive demand from the modelling perspective is required. Hence, the main objective of this paper is to forecast the demand of automotive Proton car industry in Malaysia using system dynamics approach. Two types of intervention namely optimistic and pessimistic experiments scenarios have been tested to determine the capacity expansion that can prevent the company from overstocking. Finding from this study highlighted that the management needs to expand their production for optimistic scenario, whilst pessimistic give results that would otherwise. Finally, this study could help Proton Edar Sdn. Bhd (PESB) to manage the long-term capacity planning in order to meet the future demand of the Proton cars.
Demand forecasting for automotive sector in Malaysia by system dynamics approach
NASA Astrophysics Data System (ADS)
Zulkepli, Jafri; Fong, Chan Hwa; Abidin, Norhaslinda Zainal
2015-12-01
In general, Proton as an automotive company needs to forecast future demand of the car to assist in decision making related to capacity expansion planning. One of the forecasting approaches that based on judgemental or subjective factors is normally used to forecast the demand. As a result, demand could be overstock that eventually will increase the operation cost; or the company will face understock, which resulted losing their customers. Due to automotive industry is very challenging process because of high level of complexity and uncertainty involved in the system, an accurate tool to forecast the future of automotive demand from the modelling perspective is required. Hence, the main objective of this paper is to forecast the demand of automotive Proton car industry in Malaysia using system dynamics approach. Two types of intervention namely optimistic and pessimistic experiments scenarios have been tested to determine the capacity expansion that can prevent the company from overstocking. Finding from this study highlighted that the management needs to expand their production for optimistic scenario, whilst pessimistic give results that would otherwise. Finally, this study could help Proton Edar Sdn. Bhd (PESB) to manage the long-term capacity planning in order to meet the future demand of the Proton cars.
A systems biology approach to cancer: fractals, attractors, and nonlinear dynamics.
Dinicola, Simona; D'Anselmi, Fabrizio; Pasqualato, Alessia; Proietti, Sara; Lisi, Elisabetta; Cucina, Alessandra; Bizzarri, Mariano
2011-03-01
Cancer begins to be recognized as a highly complex disease, and advanced knowledge of the carcinogenic process claims to be acquired by means of supragenomic strategies. Experimental data evidence that tumor emerges from disruption of tissue architecture, and it is therefore consequential that the tissue level should be considered the proper level of observation for carcinogenic studies. This paradigm shift imposes to move from a reductionistic to a systems biology approach. Indeed, cell phenotypes are emergent modes arising through collective nonlinear interactions among different cellular and microenvironmental components, generally described by a phase space diagram, where stable states (attractors) are embedded into a landscape model. Within this framework cell states and cell transitions are generally conceived as mainly specified by the gene-regulatory network. However, the system's dynamics cannot be reduced to only the integrated functioning of the genome-proteome network, and the cell-stroma interacting system must be taken into consideration in order to give a more reliable picture. As cell form represents the spatial geometric configuration shaped by an integrated set of cellular and environmental cues participating in biological functions control, it is conceivable that fractal-shape parameters could be considered as "omics" descriptors of the cell-stroma system. Within this framework it seems that function follows form, and not the other way around.
A Dynamical System Approach to the Surface Search of Debris from MH370
NASA Astrophysics Data System (ADS)
Mancho, Ana M.; Garcia-Garrido, V. J.; Wiggins, S.; Mendoza, C.
2015-11-01
The disappearance of Malaysia Airlines flight MH370 on the morning of the 8th of March 2014 is one of the great mysteries of our time. One relevant aspect of this mystery is that not a single piece of debris from the aircraft was found during the intensive surface search carried out in the months following the crash. Difficulties in the search efforts, due to the uncertainty in the plane's final impact point and the time passed since the accident, brought the question on how the debris was scattered in an always moving ocean, for which there were multiple datasets that do not uniquely determined its state. Our approach to this problem is based on dynamical systems tools that identify dynamic barriers and coherent structures governing transport. By combining different ocean data with these mathematical techniques, we are able to assess the spatio-temporal state of the ocean in the priority search area at the time of impact and the following weeks. Using this information we propose a revised search strategy by showing why one might not have expected to find debris in some large search areas targeted by the search services and determining regions where one might have expected impact debris to be located and that have not been subjected to any exploration. This research has been supported by MINECO under grants MTM2014-56392-R and ICMAT Severo Ochoa project SEV-2011-0087 and ONR grant No. N00014- 01-1-0769. Computational support from CESGA is acknowledged.
Planning for Water Resources of South Florida: A system dynamics modeling approach
NASA Astrophysics Data System (ADS)
Ahmad, S.
2006-12-01
With enormous growth in population, changes in land use, substantial agriculture activity, and need to protect vital environmental resources such as Everglades, south Florida presents a very challenging case for water resources planning. Working with stakeholders to meet challenges of water resources planning in south Florida, we are exploring important questions: (a) What are some major changes in terms of population growth, land use, water demand, and water availability that can be expected in south Florida in the short and long term?; (b) What would be the major hydrologic effects of climate variability and change on south Florida's water system?; (c) How could Florida's water system adapt to anticipated population growth, urban sprawl, and climate change?; and (d) What are the most promising (cost effective) policies for south Florida's water management in response to growth and climate change? We are developing a decision support (DS) framework, using system dynamics modeling approach, to evaluate and compare different short and long term water management policies. Besides climate information, the integrated DS framework considers other major factors that influence water demand and availability including: demographic changes, land use changes, economy, and environment. We analyze how increased or better use of climate information can lead to better, more cost-effective decisions for sustainable management of water resources. Using games/scenarios involving decision makers, we evaluate cost-effectiveness of different policy choices for short and long term water management in the region. We evaluate policies based on both demand side management through efficiency and conservation (low flow appliances, xeriscaping, pricing) and supply side management (desalination, water reuse). The outcome is a framework for exploring cost-effectiveness of alternative water management policies. The research advances work on water resources planning considering the impacts of
Semwanga, Agnes Rwashana; Nakubulwa, Sarah; Adam, Taghreed
2016-05-04
The most recent reports on global trends in neonatal mortality continue to show alarmingly slow progress on improvements in neonatal mortality rates, with sub-Saharan Africa still lagging behind. This emphasised the urgent need to innovatively employ alternative solutions that take into account the intricate complexities of neonatal health and the health systems in which the various strategies operate. In our first paper, we empirically explored the causes of the stagnating neonatal mortality in Uganda using a dynamic synthesis methodology (DSM) approach. In this paper, we completed the last three stages of DSM, which involved the development of a quantitative (simulation) model, using STELLA modelling software. We used statistical data to populate the model. Through brainstorming sessions with stakeholders, iterations to test and validate the model were undertaken. The different strategies and policy interventions that could possibly lower neonatal mortality rates were tested using what-if analysis. Sensitivity analysis was used to determine the strategies that could have a great impact on neonatal mortality. We developed a neonatal health simulation model (NEOSIM) to explore potential interventions that could possibly improve neonatal health within a health system context. The model has four sectors, namely population, demand for services, health of the mothers and choices of clinical care. It tests the effects of various interventions validated by a number of Ugandan health practitioners, including health education campaigns, free delivery kits, motorcycle coupons, kangaroo mother care, improving neonatal resuscitation and labour management skills, and interventions to improve the mothers health, i.e. targeting malaria, anaemia and tetanus. Among the tested interventions, the package with the highest impact on reducing neonatal mortality rates was a combination of the free delivery kits in a setting where delivery services were free and motorcycle coupons to
Modified neural dynamic surface approach to output feedback of MIMO nonlinear systems.
Sun, Guofa; Li, Dongwu; Ren, Xuemei
2015-02-01
We report an adaptive output feedback dynamic surface control (DSC), maintaining the prescribed performance, for a class of uncertain nonlinear systems with multiinput and multioutput. Designing neural network observers and modifying the DSC method achieves several control objectives. First, to achieve output feedback control, the finite-time echo state networks (ESN) observer with fast convergence is designed to obtain the online system states. Thus, the immeasurable states in traditional state feedback control are estimated and the unknown functions are approximated by ESN. Then, a modified DSC approach is developed by introducing a high-order sliding mode differentiator to replace the first-order filter in each step. Thus, the effect of filter performance on closed-loop stability is reduced. Furthermore, the input to state stability guarantees that all signals of the whole closed-loop system are semiglobally uniformly ultimately bounded. Specifically, the performance functions make the tracking errors converge to a compact set around equilibrium. Two numerical examples illustrated the proposed control scheme with satisfactory results.
Eigenvalue density of linear stochastic dynamical systems: A random matrix approach
NASA Astrophysics Data System (ADS)
Adhikari, S.; Pastur, L.; Lytova, A.; Du Bois, J.
2012-02-01
Eigenvalue problems play an important role in the dynamic analysis of engineering systems modeled using the theory of linear structural mechanics. When uncertainties are considered, the eigenvalue problem becomes a random eigenvalue problem. In this paper the density of the eigenvalues of a discretized continuous system with uncertainty is discussed by considering the model where the system matrices are the Wishart random matrices. An analytical expression involving the Stieltjes transform is derived for the density of the eigenvalues when the dimension of the corresponding random matrix becomes asymptotically large. The mean matrices and the dispersion parameters associated with the mass and stiffness matrices are necessary to obtain the density of the eigenvalues in the frameworks of the proposed approach. The applicability of a simple eigenvalue density function, known as the Marenko-Pastur (MP) density, is investigated. The analytical results are demonstrated by numerical examples involving a plate and the tail boom of a helicopter with uncertain properties. The new results are validated using an experiment on a vibrating plate with randomly attached spring-mass oscillators where 100 nominally identical samples are physically created and individually tested within a laboratory framework.
Identification of time-varying structural dynamic systems - An artificial intelligence approach
NASA Technical Reports Server (NTRS)
Glass, B. J.; Hanagud, S.
1992-01-01
An application of the artificial intelligence-derived methodologies of heuristic search and object-oriented programming to the problem of identifying the form of the model and the associated parameters of a time-varying structural dynamic system is presented in this paper. Possible model variations due to changes in boundary conditions or configurations of a structure are organized into a taxonomy of models, and a variant of best-first search is used to identify the model whose simulated response best matches that of the current physical structure. Simulated model responses are verified experimentally. An output-error approach is used in a discontinuous model space, and an equation-error approach is used in the parameter space. The advantages of the AI methods used, compared with conventional programming techniques for implementing knowledge structuring and inheritance, are discussed. Convergence conditions and example problems have been discussed. In the example problem, both the time-varying model and its new parameters have been identified when changes occur.
Identification of time-varying structural dynamic systems - An artificial intelligence approach
NASA Technical Reports Server (NTRS)
Glass, B. J.; Hanagud, S.
1992-01-01
An application of the artificial intelligence-derived methodologies of heuristic search and object-oriented programming to the problem of identifying the form of the model and the associated parameters of a time-varying structural dynamic system is presented in this paper. Possible model variations due to changes in boundary conditions or configurations of a structure are organized into a taxonomy of models, and a variant of best-first search is used to identify the model whose simulated response best matches that of the current physical structure. Simulated model responses are verified experimentally. An output-error approach is used in a discontinuous model space, and an equation-error approach is used in the parameter space. The advantages of the AI methods used, compared with conventional programming techniques for implementing knowledge structuring and inheritance, are discussed. Convergence conditions and example problems have been discussed. In the example problem, both the time-varying model and its new parameters have been identified when changes occur.
Statistical dynamics of classical systems: A self-consistent field approach
Grzetic, Douglas J. Wickham, Robert A.; Shi, An-Chang
2014-06-28
We develop a self-consistent field theory for particle dynamics by extremizing the functional integral representation of a microscopic Langevin equation with respect to the collective fields. Although our approach is general, here we formulate it in the context of polymer dynamics to highlight satisfying formal analogies with equilibrium self-consistent field theory. An exact treatment of the dynamics of a single chain in a mean force field emerges naturally via a functional Smoluchowski equation, while the time-dependent monomer density and mean force field are determined self-consistently. As a simple initial demonstration of the theory, leaving an application to polymer dynamics for future work, we examine the dynamics of trapped interacting Brownian particles. For binary particle mixtures, we observe the kinetics of phase separation.
NASA Astrophysics Data System (ADS)
Casanova, R.; Mendialdua, J.
1997-11-01
The importance of using non-inertial reference systems in some problems of translational dynamics is addressed. For this, a problem is presented with its detailed solution. Typical misconceptions and preconceptions of students in this subject are discussed.
Computational dynamics for robotics systems using a non-strict computational approach
NASA Technical Reports Server (NTRS)
Orin, David E.; Wong, Ho-Cheung; Sadayappan, P.
1989-01-01
A Non-Strict computational approach for real-time robotics control computations is proposed. In contrast to the traditional approach to scheduling such computations, based strictly on task dependence relations, the proposed approach relaxes precedence constraints and scheduling is guided instead by the relative sensitivity of the outputs with respect to the various paths in the task graph. An example of the computation of the Inverse Dynamics of a simple inverted pendulum is used to demonstrate the reduction in effective computational latency through use of the Non-Strict approach. A speedup of 5 has been obtained when the processes of the task graph are scheduled to reduce the latency along the crucial path of the computation. While error is introduced by the relaxation of precedence constraints, the Non-Strict approach has a smaller error than the conventional Strict approach for a wide range of input conditions.
NASA Astrophysics Data System (ADS)
Adamovic, M.; Braud, I.; Branger, F.; Kirchner, J. W.
2015-05-01
This study explores how catchment heterogeneity and variability can be summarized in simplified models, representing the dominant hydrological processes. It focuses on Mediterranean catchments, characterized by heterogeneous geology, pedology and land use, as well as steep topography and a rainfall regime in which summer droughts contrast with high-rainfall periods in autumn. The Ardeche catchment (Southeast France), typical of this environment, is chosen to explore the following questions: (1) can such a Mediterranean catchment be adequately characterized by a simple dynamical systems approach and what are the limits of the method under such conditions? (2) what information about dominant predictors of hydrological variability can be retrieved from this analysis in such catchments? In this work we apply the data-driven approach of Kirchner (2009) to estimate discharge sensitivity functions that summarize the behaviour of four sub-catchments of the Ardeche, using low-vegetation periods (November-March) from 9 years of measurements (2000-2008) from operational networks. The relevance of the inferred sensitivity function is assessed through hydrograph simulations, and through estimating precipitation rates from discharge fluctuations. We find that the discharge sensitivity function is downward-curving in double-logarithmic space, thus allowing further simulation of discharge and non-divergence of the model, only during low-vegetation periods. The analysis is complemented by a Monte Carlo sensitivity analysis showing how the parameters summarizing the discharge sensitivity function impact the simulated hydrographs. The resulting discharge simulation results are good for granite catchments, which are likely to be characterized by shallow subsurface flow at the interface between soil and bedrock. The simple dynamical system hypothesis works especially well in wet conditions (peaks and recessions are well modelled). On the other hand, poor model performance is associated
A System Dynamics Approach for the Selection of Contaminated Land Management Options
NASA Astrophysics Data System (ADS)
McKnight, U. S.; Kuebert, M.; Finkel, M.; Bieg, M.
2006-12-01
Large-scale contaminated land and groundwater is a widespread problem that can severely impact human health, the environment and the economy at many urban sites all over the world. Usually a considerable number of potential management solutions exist at each of these sites. A detailed investigation of all these options, however, is not economically feasible which makes streamlining of the planning and decision process a mandatory requirement. Decisions to be taken should be made as early as possible in order to reduce expenditures on site investigation. Therefore, a tiered decision-making procedure is required, including (i) identification and prioritization of focal areas of risks, (ii) feasibility screening of remediation targets and available management alternatives to narrow the range of possible options for (iii) subsequent detailed investigations of only a select group of preferable options. For each of these elements, tailored decision and investigation concepts are required. These concepts and applied methods should be specifically adapted to the type and scale of the particular decision to be taken- more target-oriented, cost-efficient investigation programs, as well as model-based assessment methods are needed (Ruegner et al. 2006). A gap exists within this framework with respect to preliminary assessment methodologies representing the first decision level. To fill this gap, a new system dynamics approach has been developed that represents the system of source- pathway-receptor sequences by means of a mass flux model. The dynamics are governed by the effects of possible remedial actions, which are described as mass flux change over time (Serapiglia et al. 2005). This approach has been implemented in the preliminary evaluation tool CARO-plus (Cost-efficiency Assessment of Remediation Options) that models the effects of potential remedial actions, including tackling the contaminant source and managing the groundwater plume. The model represents the causal
An Unscented Kalman Filter Approach to the Estimation of Nonlinear Dynamical Systems Models
ERIC Educational Resources Information Center
Chow, Sy-Miin; Ferrer, Emilio; Nesselroade, John R.
2007-01-01
In the past several decades, methodologies used to estimate nonlinear relationships among latent variables have been developed almost exclusively to fit cross-sectional models. We present a relatively new estimation approach, the unscented Kalman filter (UKF), and illustrate its potential as a tool for fitting nonlinear dynamic models in two ways:…
An Unscented Kalman Filter Approach to the Estimation of Nonlinear Dynamical Systems Models
ERIC Educational Resources Information Center
Chow, Sy-Miin; Ferrer, Emilio; Nesselroade, John R.
2007-01-01
In the past several decades, methodologies used to estimate nonlinear relationships among latent variables have been developed almost exclusively to fit cross-sectional models. We present a relatively new estimation approach, the unscented Kalman filter (UKF), and illustrate its potential as a tool for fitting nonlinear dynamic models in two ways:…
Microscopic Description of Few-Body Systems in the Fermionic Molecular Dynamics Approach
NASA Astrophysics Data System (ADS)
Neff, T.; Feldmeier, H.
2009-05-01
Fermionic Molecular Dynamics (FMD) is a microscopic approach for the description of light nuclei in the p- and sd-shell. Many-body basis states are Slater determinants of Gaussian wave-packets localized in phase space. Brink-type cluster states and harmonic oscillator shell model states are contained as special limiting cases in FMD. The FMD approach is used to study the spectrum of 12C with special emphasis on states with pronounced α-clustering including the Hoyle state. The FMD approach is also used to study 17Ne which is a candidate for a two-proton halo nucleus.
Theoretical approaches for the dynamics of complex biological systems from information of networks
MOCHIZUKI, Atsushi
2016-01-01
Modern biology has provided many examples of large networks describing the interactions between multiple species of bio-molecules. It is believed that the dynamics of molecular activities based on such networks are the origin of biological functions. On the other hand, we have a limited understanding for dynamics of molecular activity based on networks. To overcome this problem, we have developed two structural theories, by which the important aspects of the dynamical properties of the system are determined only from information on the network structure, without assuming other quantitative details. The first theory, named Linkage Logic, determines a subset of molecules in regulatory networks, by which any long-term dynamical behavior of the whole system can be identified/controlled. The second theory, named Structural Sensitivity Analysis, determines the sensitivity responses of the steady state of chemical reaction networks to perturbations of the reaction rate. The first and second theories investigate the dynamical properties of regulatory and reaction networks, respectively. The first theory targets the attractors of the regulatory network systems, whereas the second theory applies only to the steady states of the reaction network systems, but predicts their detailed behavior. To demonstrate the utility of our methods several biological network systems, and show they are practically useful to analyze behaviors of biological systems. PMID:27725468
Hybrid numerical—experimental approach for investigation of dynamics of microcantilever relay system
NASA Astrophysics Data System (ADS)
Ostasevicius, V.; Tamulevicius, S.; Palevicius, A.; Ragulskis, M.; Palevicius, R.; Grigaliunas, V.
2005-01-01
The time average holography measurements of the vibrating microelectromechanical switch (MEMS) were performed in this study. Experimental measurement results exhibit good agreement with computer generated holographic interferogram analysis. The validation of experimental investigations versus numerical analysis provides the necessary background to analyze the dynamical characteristics of micromechanical systems in virtual numerical environments. Direct application of fringe counting techniques for reconstruction of motion from time average holograms cannot be straightforward if the analyzed micromechanical systems contain motion limiters. Modifications of a classical time average holographic technique enable qualitative analysis of MEMS and can be applied for investigation of dynamical properties of much broader classes of MEMS systems.
Slim, Henk A; Wilson, Mark R
2008-10-14
A combined parallel tempering (replica exchange) and domain decomposition approach is presented, which allows for the effective use of large numbers of processor cores (>256) on modest sized simulations of chemical systems (∼5000 sites). The approach is implemented in the gbmoldd molecular dynamics program for the simulation of coarse-grained molecular systems composed of combinations of isotropic and/or anisotropic particles. Benchmark results are presented for two test systems: a C24 united atom chain and a coarse-grained system of spherocylinders.
A Simplified Approach to Risk Assessment Based on System Dynamics: An Industrial Case Study.
Garbolino, Emmanuel; Chery, Jean-Pierre; Guarnieri, Franck
2016-01-01
Seveso plants are complex sociotechnical systems, which makes it appropriate to support any risk assessment with a model of the system. However, more often than not, this step is only partially addressed, simplified, or avoided in safety reports. At the same time, investigations have shown that the complexity of industrial systems is frequently a factor in accidents, due to interactions between their technical, human, and organizational dimensions. In order to handle both this complexity and changes in the system over time, this article proposes an original and simplified qualitative risk evaluation method based on the system dynamics theory developed by Forrester in the early 1960s. The methodology supports the development of a dynamic risk assessment framework dedicated to industrial activities. It consists of 10 complementary steps grouped into two main activities: system dynamics modeling of the sociotechnical system and risk analysis. This system dynamics risk analysis is applied to a case study of a chemical plant and provides a way to assess the technological and organizational components of safety. © 2016 Society for Risk Analysis.
NASA Astrophysics Data System (ADS)
Wang, Guochao; Wang, Jun
2017-01-01
We make an approach on investigating the fluctuation behaviors of financial volatility duration dynamics. A new concept of volatility two-component range intensity (VTRI) is developed, which constitutes the maximal variation range of volatility intensity and shortest passage time of duration, and can quantify the investment risk in financial markets. In an attempt to study and describe the nonlinear complex properties of VTRI, a random agent-based financial price model is developed by the finite-range interacting biased voter system. The autocorrelation behaviors and the power-law scaling behaviors of return time series and VTRI series are investigated. Then, the complexity of VTRI series of the real markets and the proposed model is analyzed by Fuzzy entropy (FuzzyEn) and Lempel-Ziv complexity. In this process, we apply the cross-Fuzzy entropy (C-FuzzyEn) to study the asynchrony of pairs of VTRI series. The empirical results reveal that the proposed model has the similar complex behaviors with the actual markets and indicate that the proposed stock VTRI series analysis and the financial model are meaningful and feasible to some extent.
Wang, Guochao; Wang, Jun
2017-01-01
We make an approach on investigating the fluctuation behaviors of financial volatility duration dynamics. A new concept of volatility two-component range intensity (VTRI) is developed, which constitutes the maximal variation range of volatility intensity and shortest passage time of duration, and can quantify the investment risk in financial markets. In an attempt to study and describe the nonlinear complex properties of VTRI, a random agent-based financial price model is developed by the finite-range interacting biased voter system. The autocorrelation behaviors and the power-law scaling behaviors of return time series and VTRI series are investigated. Then, the complexity of VTRI series of the real markets and the proposed model is analyzed by Fuzzy entropy (FuzzyEn) and Lempel-Ziv complexity. In this process, we apply the cross-Fuzzy entropy (C-FuzzyEn) to study the asynchrony of pairs of VTRI series. The empirical results reveal that the proposed model has the similar complex behaviors with the actual markets and indicate that the proposed stock VTRI series analysis and the financial model are meaningful and feasible to some extent.
Hock, Karlo; Ng, Kah Loon; Fefferman, Nina H.
2010-01-01
Social networks can be used to represent group structure as a network of interacting components, and also to quantify both the position of each individual and the global properties of a group. In a series of simulation experiments based on dynamic social networks, we test the prediction that social behaviors that help individuals reach prominence within their social group may conflict with their potential to benefit from their social environment. In addition to cases where individuals were able to benefit from improving both their personal relative importance and group organization, using only simple rules of social affiliation we were able to obtain results in which individuals would face a trade-off between these factors. While selection would favor (or work against) social behaviors that concordantly increase (or decrease, respectively) fitness at both individual and group level, when these factors conflict with each other the eventual selective pressure would depend on the relative returns individuals get from their social environment and their position within it. The presented results highlight the importance of a systems approach to studying animal sociality, in which the effects of social behaviors should be viewed not only through the benefits that those provide to individuals, but also in terms of how they affect broader social environment and how in turn this is reflected back on an individual's fitness. PMID:21203425
Frank, T D; Michelbrink, M; Beckmann, H; Schöllhorn, W I
2008-01-01
Differential learning is a learning concept that assists subjects to find individual optimal performance patterns for given complex motor skills. To this end, training is provided in terms of noisy training sessions that feature a large variety of between-exercises differences. In several previous experimental studies it has been shown that performance improvement due to differential learning is higher than due to traditional learning and performance improvement due to differential learning occurs even during post-training periods. In this study we develop a quantitative dynamical systems approach to differential learning. Accordingly, differential learning is regarded as a self-organized process that results in the emergence of subject- and context-dependent attractors. These attractors emerge due to noise-induced bifurcations involving order parameters in terms of learning rates. In contrast, traditional learning is regarded as an externally driven process that results in the emergence of environmentally specified attractors. Performance improvement during post-training periods is explained as an hysteresis effect. An order parameter equation for differential learning involving a fourth-order polynomial potential is discussed explicitly. New predictions concerning the relationship between traditional and differential learning are derived.
Sivasamy, Aneetha Avalappampatty; Sundan, Bose
2015-01-01
The ever expanding communication requirements in today's world demand extensive and efficient network systems with equally efficient and reliable security features integrated for safe, confident, and secured communication and data transfer. Providing effective security protocols for any network environment, therefore, assumes paramount importance. Attempts are made continuously for designing more efficient and dynamic network intrusion detection models. In this work, an approach based on Hotelling's T(2) method, a multivariate statistical analysis technique, has been employed for intrusion detection, especially in network environments. Components such as preprocessing, multivariate statistical analysis, and attack detection have been incorporated in developing the multivariate Hotelling's T(2) statistical model and necessary profiles have been generated based on the T-square distance metrics. With a threshold range obtained using the central limit theorem, observed traffic profiles have been classified either as normal or attack types. Performance of the model, as evaluated through validation and testing using KDD Cup'99 dataset, has shown very high detection rates for all classes with low false alarm rates. Accuracy of the model presented in this work, in comparison with the existing models, has been found to be much better.
Avalappampatty Sivasamy, Aneetha; Sundan, Bose
2015-01-01
The ever expanding communication requirements in today's world demand extensive and efficient network systems with equally efficient and reliable security features integrated for safe, confident, and secured communication and data transfer. Providing effective security protocols for any network environment, therefore, assumes paramount importance. Attempts are made continuously for designing more efficient and dynamic network intrusion detection models. In this work, an approach based on Hotelling's T2 method, a multivariate statistical analysis technique, has been employed for intrusion detection, especially in network environments. Components such as preprocessing, multivariate statistical analysis, and attack detection have been incorporated in developing the multivariate Hotelling's T2 statistical model and necessary profiles have been generated based on the T-square distance metrics. With a threshold range obtained using the central limit theorem, observed traffic profiles have been classified either as normal or attack types. Performance of the model, as evaluated through validation and testing using KDD Cup'99 dataset, has shown very high detection rates for all classes with low false alarm rates. Accuracy of the model presented in this work, in comparison with the existing models, has been found to be much better. PMID:26357668
The Ebola Crisis and the Corresponding Public Behavior: A System Dynamics Approach
Sharareh, Nasser; S. Sabounchi, Nasim; Sayama, Hiroki; MacDonald, Roderick
2016-01-01
Background: The interaction of several sociocultural and environmental factors during an epidemic crisis leads to behavioral responses that consequently make the crisis control a complex problem. Methods: The system dynamics approach has been adopted to study the relationships between spread of disease, public attention, situational awareness, and community’s response to the Ebola epidemic. Results: In developing different simulation models to capture the trend of death and incidence data from the World Health Organization for the Ebola outbreak, the final model has the best fit to the historical trends. Results demonstrate that the increase of quarantining rate over time due to increase in situational awareness and performing safe burials had a significant impact on the control of epidemic. However, public attention did not play a significant role. Conclusion: The best fit to historical data are achieved when behavioral factors specific to West Africa like studying the Situational Awareness and Public Attention are included in the model. However, by ignoring the sociocultural factors, the model is not able to represent the reality; therefore, in the case of any epidemics, it is necessary that all the parties and community members find the most significant behavioral factors that can curb the epidemic. PMID:27974995
NASA Astrophysics Data System (ADS)
Lowry, T. S.; Tidwell, V. C.; Cardwell, H. E.; Ockner, G.; Rea, M. T.; Primozich, D.
2006-12-01
Water managers on the Willamette River in the state of Oregon are facing a new biological opinion and potentially strict TMDL regulations for temperature that will require actions by various stakeholders over the next few decades. Considerable public planning has already been accomplished in the basin with much of the assessment and planning phases for solving the basin's problems codified in a TMDL that was issued in 2006. Various alternatives have been proposed to meet the TMDL requirement, including operational changes at US Army Corps-operated reservoirs, projects that increase stream shading or restore the floodplain or hyporheic zone, and operational or technological changes at point sources such as waste water treatment plants and pulp and paper plants. To help meet the TMDL in a shorter time horizon, a collection of stakeholders formed the Willamette Partnership to develop an ecosystem marketplace where water quality and conservation credits can be traded. The marketplace will develop currencies in temperature and other environmental goods and services, and requires tools to describe linkages between credit trades, water operations, and other management changes (e.g. increases in stream shading) that control water temperature. These tools will link basin hydrology to temperature, water quality, and other concerns using a systems dynamics approach to provide real-time feedback to support conflict negotiation and decision making. Here, we present the development and conceptualization of those tools and their use in evaluating the potential and implementation of the ecosystem marketplace.
Hock, Karlo; Ng, Kah Loon; Fefferman, Nina H
2010-12-23
Social networks can be used to represent group structure as a network of interacting components, and also to quantify both the position of each individual and the global properties of a group. In a series of simulation experiments based on dynamic social networks, we test the prediction that social behaviors that help individuals reach prominence within their social group may conflict with their potential to benefit from their social environment. In addition to cases where individuals were able to benefit from improving both their personal relative importance and group organization, using only simple rules of social affiliation we were able to obtain results in which individuals would face a trade-off between these factors. While selection would favor (or work against) social behaviors that concordantly increase (or decrease, respectively) fitness at both individual and group level, when these factors conflict with each other the eventual selective pressure would depend on the relative returns individuals get from their social environment and their position within it. The presented results highlight the importance of a systems approach to studying animal sociality, in which the effects of social behaviors should be viewed not only through the benefits that those provide to individuals, but also in terms of how they affect broader social environment and how in turn this is reflected back on an individual's fitness.
Sayed-Hossein Sadeghi; Troy R. Peters; Mohammad Z. Amini; Sparkle L. Malone; Hank W. Loescher
2015-01-01
The increased need for water and food security requires the development of new approaches to save water through irrigation management strategies, particularly for center pivot irrigation. To do so entails monitoring of the dynamic variation in wind drift and evaporation losses (WDELs) of irrigation systems under different weather conditions and for relatively long time...
A Hybrid Systems Approach to Hormonal Therapy of Prostate Cancer and its Nonlinear Dynamics
Aihara, Kazuyuki; Tanaka, Gouhei; Suzuki, Taiji; Hirata, Yoshito
2007-07-13
This talk is to review our recent work on mathematical modeling of prostate cancer and its application to hormonal therapy of intermittent androgen suppression. First, we model the tumor growth of prostate cancer composed of a mixed dynamical assembly of androgen-dependent and androgen-independent cancer cells. Then, we introduce the intermittent androgen suppression to the model as feedback control with monitoring the serum prostate-specific antigen, where the controlled model is described as a hybrid system with continuous and discrete variables. Next, we analyze nonlinear dynamics and bifurcations of the hybrid system. Finally, we discuss a possibility to improve the hormonal therapy.
ERIC Educational Resources Information Center
Dorça, Fabiano Azevedo; Lima, Luciano Vieira; Fernandes, Márcia Aparecida; Lopes, Carlos Roberto
2012-01-01
Considering learning and how to improve students' performances, an adaptive educational system must know how an individual learns best. In this context, this work presents an innovative approach for student modeling through probabilistic learning styles combination. Experiments have shown that our approach is able to automatically detect and…
Kollikkathara, Naushad; Feng, Huan; Yu, Danlin
2010-11-01
As planning for sustainable municipal solid waste management has to address several inter-connected issues such as landfill capacity, environmental impacts and financial expenditure, it becomes increasingly necessary to understand the dynamic nature of their interactions. A system dynamics approach designed here attempts to address some of these issues by fitting a model framework for Newark urban region in the US, and running a forecast simulation. The dynamic system developed in this study incorporates the complexity of the waste generation and management process to some extent which is achieved through a combination of simpler sub-processes that are linked together to form a whole. The impact of decision options on the generation of waste in the city, on the remaining landfill capacity of the state, and on the economic cost or benefit actualized by different waste processing options are explored through this approach, providing valuable insights into the urban waste-management process.
Kollikkathara, Naushad; Feng Huan; Yu Danlin
2010-11-15
As planning for sustainable municipal solid waste management has to address several inter-connected issues such as landfill capacity, environmental impacts and financial expenditure, it becomes increasingly necessary to understand the dynamic nature of their interactions. A system dynamics approach designed here attempts to address some of these issues by fitting a model framework for Newark urban region in the US, and running a forecast simulation. The dynamic system developed in this study incorporates the complexity of the waste generation and management process to some extent which is achieved through a combination of simpler sub-processes that are linked together to form a whole. The impact of decision options on the generation of waste in the city, on the remaining landfill capacity of the state, and on the economic cost or benefit actualized by different waste processing options are explored through this approach, providing valuable insights into the urban waste-management process.
Lehman, Li-wei; Ghassemi, Mohammad; Snoek, Jasper; Nemati, Shamim
2016-01-01
In this work, we propose a stacked switching vector-autoregressive (SVAR)-CNN architecture to model the changing dynamics in physiological time series for patient prognosis. The SVAR-layer extracts dynamical features (or modes) from the time-series, which are then fed into the CNN-layer to extract higher-level features representative of transition patterns among the dynamical modes. We evaluate our approach using 8-hours of minute-by-minute mean arterial blood pressure (BP) from over 450 patients in the MIMIC-II database. We modeled the time-series using a third-order SVAR process with 20 modes, resulting in first-level dynamical features of size 20×480 per patient. A fully connected CNN is then used to learn hierarchical features from these inputs, and to predict hospital mortality. The combined CNN/SVAR approach using BP time-series achieved a median and interquartile-range AUC of 0.74 [0.69, 0.75], significantly outperforming CNN-alone (0.54 [0.46, 0.59]), and SVAR-alone with logistic regression (0.69 [0.65, 0.72]). Our results indicate that including an SVAR layer improves the ability of CNNs to classify nonlinear and nonstationary time-series. PMID:27790623
Introducing Systems Approaches
NASA Astrophysics Data System (ADS)
Reynolds, Martin; Holwell, Sue
Systems Approaches to Managing Change brings together five systems approaches to managing complex issues, each having a proven track record of over 25 years. The five approaches are: System Dynamics (SD) developed originally in the late 1950s by Jay Forrester Viable Systems Model (VSM) developed originally in the late 1960s by Stafford Beer Strategic Options Development and Analysis (SODA: with cognitive mapping) developed originally in the 1970s by Colin Eden Soft Systems Methodology (SSM) developed originally in the 1970s by Peter Checkland Critical Systems Heuristics (CSH) developed originally in the late 1970s by Werner Ulrich
Dynamic Approaches to Language Processing
ERIC Educational Resources Information Center
Srinivasan, Narayanan
2007-01-01
Symbolic rule-based approaches have been a preferred way to study language and cognition. Dissatisfaction with rule-based approaches in the 1980s lead to alternative approaches to study language, the most notable being the dynamic approaches to language processing. Dynamic approaches provide a significant alternative by not being rule-based and…
Stability of linear dynamic systems over the packet erasure channel: a co-design approach
NASA Astrophysics Data System (ADS)
Farhadi, Alireza
2015-12-01
This paper is concerned with the stability of linear time-invariant dynamic systems over the packet erasure channel subject to minimum bit rate constraint when an encoder and a decoder are unaware of the control signal. This assumption results in co-designing the encoder, decoder and controller. The encoder, decoder, controller and conditions relating transmission rate to packet erasure probability and eigenvalues of the system matrix A are presented for almost sure asymptotic stability of linear time-invariant dynamic systems over the packet erasure channel with feedback acknowledgment. When the eigenvalues of the system matrix A are real valued, it is shown that the obtained condition for stability is tight. Simulation result illustrates the satisfactory performance of the proposed encoder, decoder and controller for almost sure asymptotic stability.
Metabasin approach for computing the master equation dynamics of systems with broken ergodicity.
Mauro, John C; Loucks, Roger J; Gupta, Prabhat K
2007-08-16
We propose a technique for computing the master equation dynamics of systems with broken ergodicity. The technique involves a partitioning of the system into components, or metabasins, where the relaxation times within a metabasin are short compared to an observation time scale. In this manner, equilibrium statistical mechanics is assumed within each metabasin, and the intermetabasin dynamics are computed using a reduced set of master equations. The number of metabasins depends upon both the temperature of the system and its derivative with respect to time. With this technique, the integration time step of the master equations is governed by the observation time scale rather than the fastest transition time between basins. We illustrate the technique using a simple model landscape with seven basins and show validation against direct Euler integration. Finally, we demonstrate the use of the technique for a realistic glass-forming system (viz., selenium) where direct Euler integration is not computationally feasible.
Toward a Comprehensive Model of Antisocial Development: A Dynamic Systems Approach
ERIC Educational Resources Information Center
Granic, Isabela; Patterson, Gerald R.
2006-01-01
The purpose of this article is to develop a preliminary comprehensive model of antisocial development based on dynamic systems principles. The model is built on the foundations of behavioral research on coercion theory. First, the authors focus on the principles of multistability, feedback, and nonlinear causality to reconceptualize real-time…
ERIC Educational Resources Information Center
Eynde, Peter Op 't; Turner, Jeannine E.
2006-01-01
Understanding the interrelations among students' cognitive, emotional, motivational, and volitional processes is an emergening focus in educational psychology. A dynamical, component systems theory of emotions is presented as a promising framework to further unravel these complex interrelations. This framework considers emotions to be a process…
A dynamical systems approach to actin-based motility in Listeria monocytogenes
NASA Astrophysics Data System (ADS)
Hotton, S.
2010-11-01
A simple kinematic model for the trajectories of Listeria monocytogenes is generalized to a dynamical system rich enough to exhibit the resonant Hopf bifurcation structure of excitable media and simple enough to be studied geometrically. It is shown how L. monocytogenes trajectories and meandering spiral waves are organized by the same type of attracting set.
Understanding the Online Informal Learning of English as a Complex Dynamic System: An Emic Approach
ERIC Educational Resources Information Center
Sockett, Geoffrey
2013-01-01
Research into the online informal learning of English has already shown it to be a widespread phenomenon involving a range of comprehension and production activities such as viewing original version television series, listening to music on demand and social networking with other English users. Dynamic systems theory provides a suitable framework…
Jason, Leonard A.; Stevens, Edward B.; Callahan, Sarah; Stone, Ariel
2015-01-01
The complex system conception of group social dynamics often involves not only changing individual characteristics, but also changing within-group relationships. Recent advances in stochastic dynamic network modeling allow these interdependencies to be modeled from data. This methodology is discussed within a context of other mathematical and statistical approaches that have been or could be applied to study the temporal evolution of relationships and behaviors within small- to medium-sized groups. An example model is presented, based on a pilot study of five Oxford House recovery homes, sober living environments for individuals following release from acute substance abuse treatment. This model demonstrates how dynamic network modeling can be applied to such systems, examines and discusses several options for pooling, and shows how results are interpreted in line with complex system concepts. Results suggest that this approach (a) is a credible modeling framework for studying group dynamics even with limited data, (b) improves upon the most common alternatives, and (c) is especially well-suited to complex system conceptions. Continuing improvements in stochastic models and associated software may finally lead to mainstream use of these techniques for the study of group dynamics, a shift already occurring in related fields of behavioral science. PMID:27065722
Light, John M; Jason, Leonard A; Stevens, Edward B; Callahan, Sarah; Stone, Ariel
2016-03-01
The complex system conception of group social dynamics often involves not only changing individual characteristics, but also changing within-group relationships. Recent advances in stochastic dynamic network modeling allow these interdependencies to be modeled from data. This methodology is discussed within a context of other mathematical and statistical approaches that have been or could be applied to study the temporal evolution of relationships and behaviors within small- to medium-sized groups. An example model is presented, based on a pilot study of five Oxford House recovery homes, sober living environments for individuals following release from acute substance abuse treatment. This model demonstrates how dynamic network modeling can be applied to such systems, examines and discusses several options for pooling, and shows how results are interpreted in line with complex system concepts. Results suggest that this approach (a) is a credible modeling framework for studying group dynamics even with limited data, (b) improves upon the most common alternatives, and (c) is especially well-suited to complex system conceptions. Continuing improvements in stochastic models and associated software may finally lead to mainstream use of these techniques for the study of group dynamics, a shift already occurring in related fields of behavioral science.
The emergence of learning-teaching trajectories in education: a complex dynamic systems approach.
Steenbeek, Henderien; van Geert, Paul
2013-04-01
In this article we shall focus on learning-teaching trajectories ='successful' as well as 'unsuccessful' ones - as emergent and dynamic phenomena resulting from the interactions in the entire educational context, in particular the interaction between students and teachers viewed as processes of intertwining self-, other- and co-regulation. The article provides a review of the educational research literature on action regulation in learning and teaching, and interprets this literature in light of the theory of complex dynamic systems. Based on this reinterpretation of the literature, two dynamic models are proposed, one focusing on the short-term dynamics of learning-teaching interactions as they take place in classrooms, the other focusing on the long-term dynamics of interactions in a network of variables encompassing concerns, evaluations, actions and action effects (such as learning) students and teachers. The aim of presenting these models is to demonstrate, first, the possibility of transforming existing educational theory into dynamic models and, second, to provide some suggestions as to how such models can be used to further educational theory and practice.
An SSM-Based Approach to Implement a Dynamic Performance Management System
NASA Astrophysics Data System (ADS)
da Piedade Francisco, Roberto; Azevedo, Américo
This paper underlines how the use of Soft Systems Methodology (SSM) for an efficient planning, implementation and monitoring of a dynamic performance management system supported by a conceptual scheme that enables a conscious and prepared implementation, can provide instances of performance of a collaborative network, and also promote alignment among the partners. A systematic way to implement it and a review on two practical applications in Brazilian collaborative networks of SMEs are also presented.
McKinney, B A; Crowe, J E; Voss, H U; Crooke, P S; Barney, N; Moore, J H
2006-02-01
We introduce a grammar-based hybrid approach to reverse engineering nonlinear ordinary differential equation models from observed time series. This hybrid approach combines a genetic algorithm to search the space of model architectures with a Kalman filter to estimate the model parameters. Domain-specific knowledge is used in a context-free grammar to restrict the search space for the functional form of the target model. We find that the hybrid approach outperforms a pure evolutionary algorithm method, and we observe features in the evolution of the dynamical models that correspond with the emergence of favorable model components. We apply the hybrid method to both artificially generated time series and experimentally observed protein levels from subjects who received the smallpox vaccine. From the observed data, we infer a cytokine protein interaction network for an individual's response to the smallpox vaccine.
NASA Astrophysics Data System (ADS)
McKinney, B. A.; Crowe, J. E., Jr.; Voss, H. U.; Crooke, P. S.; Barney, N.; Moore, J. H.
2006-02-01
We introduce a grammar-based hybrid approach to reverse engineering nonlinear ordinary differential equation models from observed time series. This hybrid approach combines a genetic algorithm to search the space of model architectures with a Kalman filter to estimate the model parameters. Domain-specific knowledge is used in a context-free grammar to restrict the search space for the functional form of the target model. We find that the hybrid approach outperforms a pure evolutionary algorithm method, and we observe features in the evolution of the dynamical models that correspond with the emergence of favorable model components. We apply the hybrid method to both artificially generated time series and experimentally observed protein levels from subjects who received the smallpox vaccine. From the observed data, we infer a cytokine protein interaction network for an individual’s response to the smallpox vaccine.
Perturbation approach and the constant of motion for on-dimensional dynamical systems
Lopez, G.
1991-11-01
A perturbation technic is used to find the constant of motion of a one-dimensional autonomous system. The convergence of the method is discussed through some examples. In addition, the approach is extended to one-dimensional non-autonomous systems where some examples are given.
Lee, M T; Chang, Y C
2006-01-01
A sustainable aquatic environment, which relates to the issues of pollution mitigation and ecological restoration, is one of the important indicators of the vitality and prosperity of a city. Traditionally, resort to engineering efforts is always the first priority in dealing with such problems. Nevertheless, treated as an integrated system, the nature of the problem should involve many aspects including economic, ecological, environmental, and engineering factors. Meanwhile, the special feature of the time-dependent state has also made such a system a dynamic and complex problem. The current research has employed the concepts of integrated assessment trying to aggregate related studies and tackling the problem as a complete system. With the aid of the system dynamic modeling tool, which is capable of dealing with dynamic and complex problems, the simulation model was formulated following the macrostructure of system behavior. Various strategies for improving the sustainability of the aquatic environment in Love River, Kaohsiung, Taiwan have been evaluated. The decision makers are therefore allowed to choose more effective strategies based on the integrated perspectives.
Dynamical systems game theory II. A new approach to the problem of the social dilemma
NASA Astrophysics Data System (ADS)
Akiyama, Eizo; Kaneko, Kunihiko
2002-07-01
The “social dilemma” is a problem inherent in forming and maintaining cooperation among selfish individuals, and is of fundamental importance in the biological and social sciences. From the viewpoint of traditional game theory, the existence of the social dilemma necessarily implies degeneration into selfish behavior as the numbers of members in a community increases, unless there exists some external power. In the real world, however, cooperation is often formed and maintained merely through mutual interactions, without the influence of an external power. To answer questions concerning appearance and maintenance of cooperative behavior in societies, we study what we call the “Lumberjacks’ Dilemma (LD) game”, as an application of the dynamical systems (DS) game theory presented in [Physica D 147 (2000) 221], which can naturally deal with the dynamic aspects of games. Dynamical processes that lead to the formation and maintenance of cooperation, which is often observed in the real communities, are realized in our model. The mechanism underlying this formation and maintenance is explained from the DS game point of view, by analyzing the functional dependence of the attractor of the game dynamics on a parameter characterizing the strategy. It is demonstrated that norms for cooperation are formed as strategies that are manifested as specific attractors of game dynamics. The change in the stability of this cooperative behavior as the number of members increases is also discussed. Finally, the relevance of our study to cooperation seen in the real world is discussed.
NASA Astrophysics Data System (ADS)
Nataraju, Madhura; Johnson, Timothy J.; Adams, Douglas E.
2003-07-01
Environmental and operational variability due to changes in the excitation or any other variable can mimic or altogether obscure evidence of structural defects in measured data leading to false positive/negative diagnoses of damage and conservative/tolerant predictions of remaining useful life in structural health monitoring system. Diagnostic and prognostic errors like these in many types of commercial and defense-related applications must be eliminated if health monitoring is to be widely implemented in these applications. A theoretical framework of "dynamic similiarity" in which two sets of mathematical operators are utilized in one system/data model to distinguish damage from nonlinear, time-varying and stochastic events in the measured data is discussed in this paper. Because structural damage initiation, evolution and accumulation are nonlinear processes, the challenge here is to distinguish damage from nonlinear, time-varying and stochastic events in the measured data is discussed in this paper. Because structural damage initiation, evolution and accumulation are nonlinear processes, the challenge here is to distinguish abnormal from normal nonlinear dynamics, which are accentuated by physically or statistically non-stationary events in the operating environment. After discussing several examples of structural diagnosis and prognosis involving dynamic similarity, a simplifeid numerical finite element model of a helicopter blade with time-varying flexural stiffness on a nonlinear aerodynamic elastic foundation that is subjected to a stochastic base excitation is utilized to introduce and examine the effects of dynamic similarity on health monitoring systems. It is shown that environmental variability can be distinguished from structural damage using a physics-based model in conjunction with the dynamic similarity operators to develop more robust damage detection algorithms, which may prove to be more accurate and precise when operating conditions fluctuate.
NASA Astrophysics Data System (ADS)
Wei, Qing-Lai; Liu, De-Rong; Xu, Yan-Cai
2015-03-01
A policy iteration algorithm of adaptive dynamic programming (ADP) is developed to solve the optimal tracking control for a class of discrete-time chaotic systems. By system transformations, the optimal tracking problem is transformed into an optimal regulation one. The policy iteration algorithm for discrete-time chaotic systems is first described. Then, the convergence and admissibility properties of the developed policy iteration algorithm are presented, which show that the transformed chaotic system can be stabilized under an arbitrary iterative control law and the iterative performance index function simultaneously converges to the optimum. By implementing the policy iteration algorithm via neural networks, the developed optimal tracking control scheme for chaotic systems is verified by a simulation. Project supported by the National Natural Science Foundation of China (Grant Nos. 61034002, 61233001, 61273140, 61304086, and 61374105) and the Beijing Natural Science Foundation, China (Grant No. 4132078).
Time-dependent Hartree approaches for the study of intramolecular dynamics in dimer systems
NASA Astrophysics Data System (ADS)
Roy, Pierre-Nicholas; Light, John C.
2000-06-01
We apply and the time-dependent Hartree (TDH) method to the study of intramolecular dynamics in dimer systems. The HCl dimer is chosen as test case. Model calculations are performed on reduced dimensional representation of this system namely two-, three-, and four-dimensional ones. We assess the validity of different implementations of the TDH method including the account of direct correlations between coordinate pairs, and mixed quantum-classical and quantum-Gaussian wave packets treatments. The latter yields very good results compared to the fully quantal treatment.
Whole Building Design Objectives for Campus Safety and Security: A System Dynamics Approach
ERIC Educational Resources Information Center
Oakes, Charles G.
2010-01-01
The May/June 2009 issue of "Facilities Manager" introduced APPA readers to the Whole Building Design Guide (WBDG)--today's most comprehensive Internet-based depository of resources contributing to a systems approach for everything of a building nature. The emphasis in that article was on Operations and Maintenance (O&M) issues and procedures. In…
NASA Astrophysics Data System (ADS)
Chang, Wei-Der; Yan, Jun-Juh
2006-10-01
In this paper, we propose a novel genetic algorithm (GA) with a multi-crossover fashion to estimate the associated coefficients for a class of nonlinear discrete-time multivariable dynamical systems. Unlike the traditional crossover method of using two chromosomes, the proposed method uses three chromosomes to achieve a crossover. According to the adjusting direction by crossing three chromosomes, more excellent offspring can be produced. To solve the identification problem of multivariable nonlinear discrete-time systems, each of estimated system coefficients represents a gene, and a collection of genes is referred to as a chromosome in the view of GA. The chromosomes in the population are then evolved using the proposed multi-crossover method. An illustrative example of multivariable nonlinear systems is given to demonstrate the effectiveness, as compared with the traditional crossover method, of the proposed method.
2007-11-02
modeler uses a system dynamics approach to construct a model that represents behavior in the iron-reducing environment. The model incorporates hematite ...incorporated into the model. Model simulations show that the organic material parameters have a greater influence on hematite depletion compared with...parameters of the modeled contaminants. By increasing the amount of hematite in the soil, the time period that biodegrading processes exist in the
Containment Control of Multiagent Systems With Dynamic Leaders Based on a $PI^{n}$ -Type Approach.
Cheng, Long; Wang, Yunpeng; Ren, Wei; Hou, Zeng-Guang; Tan, Min
2016-12-01
This paper studies the containment control of multiagent systems (MASs) with multiple dynamic leaders in both continuous-time domain and discrete-time domain. The leaders' motions are described by the n th-order polynomial trajectories. This setting makes practical sense because given some critical points, the leaders' trajectories are usually planned by the polynomial interpolations. In order to drive all followers into the convex hull spanned by the leaders, a PI (n) -type containment algorithm is proposed ( P and I are short for proportional and integral, respectively; I (n) implies that the algorithm includes up to the n th-order integral terms). It is theoretically proved that the PI (n) -type containment algorithm is able to solve the containment problem of MASs where the followers are described by any order integral dynamics. Compared to the previous results on the MASs with dynamic leaders, the distinguished features of this paper are that: 1) the containment problem is studied not only in the continuous-time domain but also in the discrete-time domain while most existing results only work in the continuous-time domain; 2) to deal with the leaders with the n th-order polynomial trajectories, existing results require the follower's dynamics to be the ( n+ 1)th-order integral while the followers considered in this paper can be described by any-order integral dynamics; 3) the "sign" function is not employed in the proposed algorithm, which avoids the chattering phenomenon; and 4) both disturbance and measurement noise are taken into account. Finally, some simulation examples are given to demonstrate the effectiveness of the proposed algorithm.
Role of transcriptional regulation in the evolution of plant phenotype: A dynamic systems approach.
Rodríguez-Mega, Emiliano; Piñeyro-Nelson, Alma; Gutierrez, Crisanto; García-Ponce, Berenice; Sánchez, María De La Paz; Zluhan-Martínez, Estephania; Álvarez-Buylla, Elena R; Garay-Arroyo, Adriana
2015-03-02
A growing body of evidence suggests that alterations in transcriptional regulation of genes involved in modulating development are an important part of phenotypic evolution, and this can be documented among species and within populations. While the effects of differential transcriptional regulation in organismal development have been preferentially studied in animal systems, this phenomenon has also been addressed in plants. In this review, we summarize evidence for cis-regulatory mutations, trans-regulatory changes and epigenetic modifications as molecular events underlying important phenotypic alterations, and thus shaping the evolution of plant development. We postulate that a mechanistic understanding of why such molecular alterations have a key role in development, morphology and evolution will have to rely on dynamic models of complex regulatory networks that consider the concerted action of genetic and nongenetic components, and that also incorporate the restrictions underlying the genotype to phenotype mapping process. Developmental Dynamics, 2015. © 2015 Wiley Periodicals, Inc.
NASA Astrophysics Data System (ADS)
Kinugawa, Kenichi; Nagao, Hidemi; Ohta, Koji
2001-01-01
We present a formalism of the path integral centroid molecular dynamics (CMD) extended to Bose and Fermi statistics as a semiclassical approach to explore the dynamics of quantum many-body systems. The validity of the method is examined in relation to the time correlation functions. The presently proposed scheme, refined from our previous derivation [Chem. Phys. Lett. 307, 187 (1999)], is aimed at the calculations of not the exact quantum-mechanical dynamics but the semiclassical dynamics under certain approximations. The formalism is based on the projection operator with which the Bose/Fermi system is mapped onto a particular type of pseudo-Boltzmann system. In the pseudo-Boltzmann system the correlation due to the Bose/Fermi statistics is introduced via an extra pseudopotential called the permutation potential and its relevant operator. Using the present semiclassical formalism, the time correlation function of centroid position, which is evaluated from the CMD trajectories in the pseudo-Boltzmann system, is an approximation to the Kubo canonical correlation function of position operator of the exact quantum-statistical system composed of bosons or fermions. There is no such apparent relation between the momentum operator and the corresponding momentum centroid.
Learning process as an interplay between understanding and doubt: A dynamical systems approach
NASA Astrophysics Data System (ADS)
Monteiro, L. H. A.; Notargiacomo, P. C. S.
2017-06-01
A relevant question related to the process of teaching and learning is: Are the doubts signals of student's failure, because they can be associated to a reduction on the comprehension, or the doubts drive the learner to acquire more knowledge, which increases the understanding on the studied material? Here, this issue is investigated by formulating and analyzing a dynamical system written in terms of differential equations. The model predicts that different levels of comprehension can be reached, depending on the initial condition. This and other results are discussed from an educational point of view.
NASA Astrophysics Data System (ADS)
Behr, Joshua G.; Diaz, Rafael
Non-urgent Emergency Department utilization has been attributed with increasing congestion in the flow and treatment of patients and, by extension, conditions the quality of care and profitability of the Emergency Department. Interventions designed to divert populations to more appropriate care may be cautiously received by operations managers due to uncertainty about the impact an adopted intervention may have on the two values of congestion and profitability. System Dynamics (SD) modeling and simulation may be used to measure the sensitivity of these two, often-competing, values of congestion and profitability and, thus, provide an additional layer of information designed to inform strategic decision making.
Linel, Patrice; Wu, Shuang; Deng, Nan
2015-01-01
Recent studies demonstrate that human blood transcriptional signatures may be used to support diagnosis and clinical decisions for acute respiratory viral infections such as influenza. In this article, we propose to use a newly developed systems biology approach for time course gene expression data to identify significant dynamically response genes and dynamic gene network responses to viral infection. We illustrate the methodological pipeline by reanalyzing the time course gene expression data from a study with healthy human subjects challenged by live influenza virus. We observed clear differences in the number of significant dynamic response genes (DRGs) between the symptomatic and asymptomatic subjects and also identified DRG signatures for symptomatic subjects with influenza infection. The 505 common DRGs shared by the symptomatic subjects have high consistency with the signature genes for predicting viral infection identified in previous works. The temporal response patterns and network response features were carefully analyzed and investigated. PMID:25015847
Linel, Patrice; Wu, Shuang; Deng, Nan; Wu, Hulin
2014-10-01
Recent studies demonstrate that human blood transcriptional signatures may be used to support diagnosis and clinical decisions for acute respiratory viral infections such as influenza. In this article, we propose to use a newly developed systems biology approach for time course gene expression data to identify significant dynamically response genes and dynamic gene network responses to viral infection. We illustrate the methodological pipeline by reanalyzing the time course gene expression data from a study with healthy human subjects challenged by live influenza virus. We observed clear differences in the number of significant dynamic response genes (DRGs) between the symptomatic and asymptomatic subjects and also identified DRG signatures for symptomatic subjects with influenza infection. The 505 common DRGs shared by the symptomatic subjects have high consistency with the signature genes for predicting viral infection identified in previous works. The temporal response patterns and network response features were carefully analyzed and investigated.
Time-resolved spectroscopy at surfaces and adsorbate dynamics: Insights from a model-system approach
NASA Astrophysics Data System (ADS)
Boström, Emil; Mikkelsen, Anders; Verdozzi, Claudio
2016-05-01
We introduce a model description of femtosecond laser induced desorption at surfaces. The substrate part of the system is taken into account as a (possibly semi-infinite) linear chain. Here, being especially interested in the early stages of dissociation, we consider a finite-size implementation of the model (i.e., a finite substrate), for which an exact numerical solution is possible. By time-evolving the many-body wave function, and also using results from a time-dependent density functional theory description for electron-nuclear systems, we analyze the competition between several surface-response mechanisms and electronic correlations in the transient and longer time dynamics under the influence of dipole-coupled fields. Our model allows us to explore how coherent multiple-pulse protocols can impact desorption in a variety of prototypical experiments.
Ambulatory Healthcare Utilization in the United States: A System Dynamics Approach
NASA Technical Reports Server (NTRS)
Diaz, Rafael; Behr, Joshua G.; Tulpule, Mandar
2011-01-01
Ambulatory health care needs within the United States are served by a wide range of hospitals, clinics, and private practices. The Emergency Department (ED) functions as an important point of supply for ambulatory healthcare services. Growth in our aging populations as well as changes stemming from broader healthcare reform are expected to continue trend in congestion and increasing demand for ED services. While congestion is, in part, a manifestation of unmatched demand, the state of the alignment between the demand for, and supply of, emergency department services affects quality of care and profitability. The central focus of this research is to provide an explanation of the salient factors at play within the dynamic demand-supply tensions within which ambulatory care is provided within an Emergency Department. A System Dynamics (SO) simulation model is used to capture the complexities among the intricate balance and conditional effects at play within the demand-supply emergency department environment. Conceptual clarification of the forces driving the elements within the system , quantifying these elements, and empirically capturing the interaction among these elements provides actionable knowledge for operational and strategic decision-making.
Kaabi, Belhassen; Ahmed, Sami Ben-hadj
2013-12-01
Capturing or diverting the disease carrying vector from humans can reduce the transmission of vector borne diseases such as leishmaniasis. The use of animals that act as dead-end hosts to relieve the vector (sandfly) bites on humans is called zooprophylaxis. However, as the number of blood meal providers especially domestic animals increases, the sandflies enhanced availability of blood meals will improve its number and survival, thereby countering the impact of diverting bites from humans. Thus, the transmission model exhibits the structure of a feedback loop characterizing complex dynamic systems. In order to rigorously assess the effect of zooprophylaxis, we propose a system dynamic model for zoonotic cutaneous leishmaniasis transmission with 3 blood-meal hosts: domestic animals, humans, and a reservoir (rodents). In this context, a simulation study of the proposed model with a follow-up period of 1000 days was performed. We explored how perturbations in the parameters characterizing the transmission, essentially the vector biting rates and the size of the domestic animal population, affect the zooprophylaxis outcome. The results show that the basic reproductive number R0 and the disease incidence in humans are decreasing function of the relative size of the domestic animal population. The speed of this decrease depends also on the vector biting rates of the different mammal species. The key factors influencing the magnitude of zooprophylaxis are: the sizes of the vector, rodent, and domestic animal populations, as well as, the biting rates which incorporate relative attraction and accessibility of the vectors to the mammalian populations.
Dynamics of open quantum spin systems: An assessment of the quantum master equation approach.
Zhao, P; De Raedt, H; Miyashita, S; Jin, F; Michielsen, K
2016-08-01
Data of the numerical solution of the time-dependent Schrödinger equation of a system containing one spin-1/2 particle interacting with a bath of up to 32 spin-1/2 particles is used to construct a Markovian quantum master equation describing the dynamics of the system spin. The procedure of obtaining this quantum master equation, which takes the form of a Bloch equation with time-independent coefficients, accounts for all non-Markovian effects inasmuch the general structure of the quantum master equation allows. Our simulation results show that, with a few rather exotic exceptions, the Bloch-type equation with time-independent coefficients provides a simple and accurate description of the dynamics of a spin-1/2 particle in contact with a thermal bath. A calculation of the coefficients that appear in the Redfield master equation in the Markovian limit shows that this perturbatively derived equation quantitatively differs from the numerically estimated Markovian master equation, the results of which agree very well with the solution of the time-dependent Schrödinger equation.
Observability-Based Approach to Design, Analysis and Optimization of Dynamical Systems
NASA Astrophysics Data System (ADS)
Alaeddini, Atiye
The present dissertation aims to use the coupling between actuation and sensing in nonlinear systems to alternatively design a set of feasible control policies, to find the minimum number of sensors, or to find an optimal sensors configuration. Feasibility, here, means a combination of sensory system and control policy which guarantees observability. In some cases the optimality of the obtained solution is also considered. In some nonlinear systems, full observability requires active sensing, and will be shown how control policies that guarantee observability can be obtained by considering the geometry of the system dynamics. The observability matrix is used to test observability, whereas for the optimization problem observability Gramian matrix is used. This dissertation also considers the stability in designing controllers. The problem of designing a stabilizing control policy for a control-affine nonlinear system is addressed. The effect of time-varying control on the observability is investigated and shown to potentially improve the system observability. A particular application of the techniques considered here is the problem of designing network sensing and topology based on the observability criteria. The goal is to develop a protocol for the network which guarantees privacy. Furthermore, given a network of connected agents, we would like to determine which nodes should be observed to maximize information about the entire network. This dissertation begins with theoretical basis then moves towards applications of the theory. The first application is navigation of an autonomous ground robot with limited inertial sensing, motivated by the visuomotor system of insects. The second application is the problem of detecting an epidemic disease, which demonstrates design of an observability-based optimal network.
NASA Astrophysics Data System (ADS)
Jin, Jinshuang; Zheng, Xiao; Yan, Yijing
2008-06-01
A generalized quantum master equation theory that governs the exact, nonperturbative quantum dissipation and quantum transport is formulated in terms of hierarchically coupled equations of motion for an arbitrary electronic system in contact with electrodes under either a stationary or a nonstationary electrochemical potential bias. The theoretical construction starts with the influence functional in path integral, in which the electron creation and annihilation operators are Grassmann variables. Time derivatives on the influence functionals are then performed in a hierarchical manner. Both the multiple-frequency dispersion and the non-Markovian reservoir parametrization schemes are considered for the desired hierarchy construction. The resulting hierarchical equations of motion formalism is in principle exact and applicable to arbitrary electronic systems, including Coulomb interactions, under the influence of arbitrary time-dependent applied bias voltage and external fields. Both the conventional quantum master equation and the real-time diagrammatic formalism of Schön and co-workers can be readily obtained at well defined limits of the present theory. We also show that for a noninteracting electron system, the present hierarchical equations of motion formalism terminates at the second tier exactly, and the Landuer-Büttiker transport current expression is recovered. The present theory renders an exact and numerically tractable tool to evaluate various transient and stationary quantum transport properties of many-electron systems, together with the involving nonperturbative dissipative dynamics.
Jin, Jinshuang; Zheng, Xiao; Yan, YiJing
2008-06-21
A generalized quantum master equation theory that governs the exact, nonperturbative quantum dissipation and quantum transport is formulated in terms of hierarchically coupled equations of motion for an arbitrary electronic system in contact with electrodes under either a stationary or a nonstationary electrochemical potential bias. The theoretical construction starts with the influence functional in path integral, in which the electron creation and annihilation operators are Grassmann variables. Time derivatives on the influence functionals are then performed in a hierarchical manner. Both the multiple-frequency dispersion and the non-Markovian reservoir parametrization schemes are considered for the desired hierarchy construction. The resulting hierarchical equations of motion formalism is in principle exact and applicable to arbitrary electronic systems, including Coulomb interactions, under the influence of arbitrary time-dependent applied bias voltage and external fields. Both the conventional quantum master equation and the real-time diagrammatic formalism of Schon and co-workers can be readily obtained at well defined limits of the present theory. We also show that for a noninteracting electron system, the present hierarchical equations of motion formalism terminates at the second tier exactly, and the Landuer-Buttiker transport current expression is recovered. The present theory renders an exact and numerically tractable tool to evaluate various transient and stationary quantum transport properties of many-electron systems, together with the involving nonperturbative dissipative dynamics.
An, Gary C
2010-01-01
The greatest challenge facing the biomedical research community is the effective translation of basic mechanistic knowledge into clinically effective therapeutics. This challenge is most evident in attempts to understand and modulate "systems" processes/disorders, such as sepsis, cancer, and wound healing. Formulating an investigatory strategy for these issues requires the recognition that these are dynamic processes. Representation of the dynamic behavior of biological systems can aid in the investigation of complex pathophysiological processes by augmenting existing discovery procedures by integrating disparate information sources and knowledge. This approach is termed Translational Systems Biology. Focusing on the development of computational models capturing the behavior of mechanistic hypotheses provides a tool that bridges gaps in the understanding of a disease process by visualizing "thought experiments" to fill those gaps. Agent-based modeling is a computational method particularly well suited to the translation of mechanistic knowledge into a computational framework. Utilizing agent-based models as a means of dynamic hypothesis representation will be a vital means of describing, communicating, and integrating community-wide knowledge. The transparent representation of hypotheses in this dynamic fashion can form the basis of "knowledge ecologies," where selection between competing hypotheses will apply an evolutionary paradigm to the development of community knowledge.
Atmospheric emissions modeling of energetic biomass alternatives using system dynamics approach
NASA Astrophysics Data System (ADS)
Szarka, Nora; Kakucs, Orsolya; Wolfbauer, Jürgen; Bezama, Alberto
To simulate the quantitative effects of regional biomass alternatives for energetic purpose (BfE) on air pollutant emissions, a system dynamics model was developed and applied for the EuRegion Austrian-Hungarian cross-border area. The dynamic simulation program Vensim ® was used to build an overall regional model with economic, social and environmental sectors. Within this model, the here-introduced regional air pollution sub-model (RegAir) includes the important human-made emissions of 10 pollutants resulting from all relevant source sectors within the region investigated. Emissions from activities related to biomass production, transport, conversion and final energy consumption were built in detail. After building and calibrating the RegAir model, seven quantitative test scenarios were defined and implemented into the model. Through the scenarios simulation, effects on air emissions were followed and compared over time. The results of these simulations show a significant reduction of CO 2 emissions, especially in cases where fossil fuel displacement in heating devices is achieved on the largest scale. On the contrary, traditional air pollutants increase by most BfE options. The results of the RegAir model simulations of BfE alternatives over two decades provide useful quantifications of various air emissions and identify the less pollutant BfE alternatives in the dynamic context of the relevant air pollution sources of the region. After minor structural modifications and appropriate calibration, RegAir can be applied to other regions as well. However, it is stated that, to finally decide on the overall most-appropriate options at a regional level, other environmental as well as economic and social effects must be taken into consideration, being the latter the goal of the mentioned overall regional model which serves as a model frame to the RegAir tool.
NASA Astrophysics Data System (ADS)
Arciniega-Ceballos, A.; Alatorre-Ibarguengoitia, M. A.; Perton, M.; Sanchez-Sesma, F. J.; Dingwell, D. B.
2012-12-01
Seismic evaluation of well-controlled experimental simulations of volumetric sources (e.g. explosions, cavitations, burst, pressure drops) is a powerful tool for better understanding of the seismic wave field of complex systems. In this work, we describe two distinct well-constrained physical models, which under controlled laboratory conditions enable the simulation of complex systems; volcanic explosions and fluid-filled wells. For volcanic explosion simulations, several experiments were performed to study seismic signals associated with fragmentation processes of volcanic rocks by rapid decompression. These experiments were performed in a shock-tube apparatus at room temperature and a pressure range of 4 to 20 MPa. Pumice samples from Popocatepetl volcano of different porosity were studied. To investigate the elastic wave propagation inside a fluid-filled well, we present a hollow cylinder model surrounded by water, excited by a ultrasonic laser beam emitting pulses between 5 and 8 ns in duration, causing micro-cavitations. Adequate instrumentation of these mechanical systems, using high-precision sensors, enabled us to capture and to analyze seismic wave fields, characterizing also their source mechanism. Although these laboratory analogues have simplified geometries and media properties, these experimental investigations are based upon the hypothesis that, in comparable systems, any physical process (e.g. pressure drops, fragmentation, vibration, elastic deformation, etc) conducts to equivalent system responses, causing the same distinctive effects, which are independent on the scale. These effects engender particular seismic signatures, reflecting the dynamics of the process, and are comparable with numerical simulations and seismic field observations. Therefore, laboratory models can validate the inverse problem solution, indicating that the source mechanism and the system nature can both be inferred from field-based seismograms.
A system dynamics approach for modeling construction workers' safety attitudes and behaviors.
Shin, Mingyu; Lee, Hyun-Soo; Park, Moonseo; Moon, Myunggi; Han, Sangwon
2014-07-01
Construction accidents are caused by an unsafe act (i.e., a person's behavior or activity that deviates from normal accepted safe procedure) and/or an unsafe condition (i.e., a hazard or an unsafe mechanical or physical environment). While there has been dramatic improvement in creating safer construction environments, relatively little is known regarding the elimination of construction workers' unsafe acts. To address this deficiency, this paper aims to develop a system dynamics (SD)-based model of construction workers' mental processes that can help analyze the feedback mechanisms and the resultant dynamics regarding the workers' safety attitudes and safe behaviors. The developed model is applied to examine the effectiveness of three safety improvement policies: incentives for safe behaviors, and increased levels of communication and immersion in accidents. Application of the model verifies the strong potential of the developed model to provide a better understanding of how to eliminate unsafe acts, and to function as a robust test-bed to assess the effectiveness of safety programs or training sessions before their implementation.
Ghaffarzadegan, Navid; Epstein, Andrew J; Martin, Erika G
2013-04-01
To simulate physician-driven dynamics of delivery mode decisions (scheduled cesarean delivery [CD] vs. vaginal delivery [VD] vs. unplanned CD after labor), and to evaluate a behavioral theory of how experiential learning leads to emerging bias toward more CD and practice variation across obstetricians. Hospital discharge data on deliveries performed by 300 randomly selected obstetricians in Florida who finished obstetrics residency and started practice after 1991. We develop a system dynamics simulation model of obstetricians' delivery mode decision based on the literature of experiential learning. We calibrate the model and investigate the extent to which the model replicates the data. Our learning-based simulation model replicates the empirical data, showing that physicians are more likely to schedule CD as they practice longer. Variation in CD rates is related to the way that physicians learn from outcomes of past decisions and accumulate experience. The repetitive nature of medical decision making, learning from past practice, and accumulating experience can account for increases in CD decisions and practice variation across physicians. Policies aimed at improving medical decision making should account for providers' feedback-based learning mechanisms. © Health Research and Educational Trust.
Finan, Patrick H.; Hessler, Eric E.; Amazeen, Polemnia G.; Butner, Jonathan; Zautra, Alex J.; Tennen, Howard
2011-01-01
Dynamical systems modeling was used to analyze fluctuations in the pain prediction process of people with rheumatoid arthritis. 170 people diagnosed with rheumatoid arthritis completed 29 consecutive days of diaries. Difference scores between pain predictions and next-day pain experience ratings provided a time series of pain prediction accuracy. Pain prediction accuracy oscillated over time. The oscillation amplitude was larger at the start of the diary than at the end, which indicates damping toward more accurate predictions. State-level psychological characteristics moderated the damping pattern such that the oscillations for patients with lower negative affect and higher pain control damped more quickly than the oscillations for their counterparts. Those findings suggest that low negative affect and high pain control generally contributed to a more accurate pain prediction process in the chronically ill. Positive affect did not differentiate the damping pattern but, within each oscillation cycle, patients with higher positive affect spent more time making inaccurate predictions than their counterparts. The current analyses highlight the need to account for change in data through dynamical modeling, which cannot be fully observed through traditional statistical techniques. PMID:20021776
Creative-Dynamics Approach To Neural Intelligence
NASA Technical Reports Server (NTRS)
Zak, Michail A.
1992-01-01
Paper discusses approach to mathematical modeling of artificial neural networks exhibiting complicated behaviors reminiscent of creativity and intelligence of biological neural networks. Neural network treated as non-Lipschitzian dynamical system - as described in "Non-Lipschitzian Dynamics For Modeling Neural Networks" (NPO-17814). System serves as tool for modeling of temporal-pattern memories and recognition of complicated spatial patterns.
Creative-Dynamics Approach To Neural Intelligence
NASA Technical Reports Server (NTRS)
Zak, Michail A.
1992-01-01
Paper discusses approach to mathematical modeling of artificial neural networks exhibiting complicated behaviors reminiscent of creativity and intelligence of biological neural networks. Neural network treated as non-Lipschitzian dynamical system - as described in "Non-Lipschitzian Dynamics For Modeling Neural Networks" (NPO-17814). System serves as tool for modeling of temporal-pattern memories and recognition of complicated spatial patterns.
Chylek, Lily A.; Harris, Leonard A.; Tung, Chang-Shung; Faeder, James R.; Lopez, Carlos F.
2013-01-01
Rule-based modeling was developed to address the limitations of traditional approaches for modeling chemical kinetics in cell signaling systems. These systems consist of multiple interacting biomolecules (e.g., proteins), which themselves consist of multiple parts (e.g., domains, linear motifs, and sites of phosphorylation). Consequently, biomolecules that mediate information processing generally have the potential to interact in multiple ways, with the number of possible complexes and post-translational modification states tending to grow exponentially with the number of binary interactions considered. As a result, only large reaction networks capture all possible consequences of the molecular interactions that occur in a cell signaling system, which is problematic because traditional modeling approaches for chemical kinetics (e.g., ordinary differential equations) require explicit network specification. This problem is circumvented through representation of interactions in terms of local rules. With this approach, network specification is implicit and model specification is concise. Concise representation results in a coarse graining of chemical kinetics, which is introduced because all reactions implied by a rule inherit the rate law associated with that rule. Coarse graining can be appropriate if interactions are modular, and the coarseness of a model can be adjusted as needed. Rules can be specified using specialized model-specification languages, and recently developed tools designed for specification of rule-based models allow one to leverage powerful software engineering capabilities. A rule-based model comprises a set of rules, which can be processed by general-purpose simulation and analysis tools to achieve different objectives (e.g., to perform either a deterministic or stochastic simulation). PMID:24123887
Modulated traveling fronts for a nonlocal Fisher-KPP equation: A dynamical systems approach
NASA Astrophysics Data System (ADS)
Faye, Grégory; Holzer, Matt
2015-04-01
We consider a nonlocal generalization of the Fisher-KPP equation in one spatial dimension. As a parameter is varied, the system undergoes a Turing bifurcation. We study the dynamics near this Turing bifurcation. Our results are two-fold. First, we prove the existence of a two-parameter family of bifurcating stationary periodic solutions and derive a rigorous asymptotic approximation of these solutions. We also study the spectral stability of the bifurcating stationary periodic solutions with respect to almost co-periodic perturbations. Second, we restrict to a specific class of exponential kernels for which the nonlocal problem is transformed into a higher order partial differential equation. In this context, we prove the existence of modulated traveling fronts near the Turing bifurcation that describe the invasion of the Turing unstable homogeneous state by the periodic pattern established in the first part. Both results rely on a center manifold reduction to a finite dimensional ordinary differential equation.
Dynamical systems approach to relativistic spherically symmetric static perfect fluid models
NASA Astrophysics Data System (ADS)
Heinzle, J. Mark; Röhr, Niklas; Uggla, Claes
2003-11-01
We investigate relativistic spherically symmetric static perfect fluid models with barotropic equations of state that are asymptotically polytropic and linear at low and high pressures, respectively. We generalize standard work on Newtonian polytropes to a relativistic setting and to a much larger class of equations of state. This is accomplished by introducing dimensionless variables that are asymptotically homology invariant in the low pressure regime, which yields a reformulation of the field equations into a regular dynamical system on a three-dimensional compact state space. A global picture of the solution space is thus obtained which makes it possible to derive qualitative features and to prove theorems about mass radius properties. Moreover, the framework is also suited for numerical computations, as illustrated by several numerical examples, e.g., the ideal neutron gas and examples that involve phase transitions.
A Bayesian nonparametric approach to reconstruction and prediction of random dynamical systems
NASA Astrophysics Data System (ADS)
Merkatas, Christos; Kaloudis, Konstantinos; Hatjispyros, Spyridon J.
2017-06-01
We propose a Bayesian nonparametric mixture model for the reconstruction and prediction from observed time series data, of discretized stochastic dynamical systems, based on Markov Chain Monte Carlo methods. Our results can be used by researchers in physical modeling interested in a fast and accurate estimation of low dimensional stochastic models when the size of the observed time series is small and the noise process (perhaps) is non-Gaussian. The inference procedure is demonstrated specifically in the case of polynomial maps of an arbitrary degree and when a Geometric Stick Breaking mixture process prior over the space of densities, is applied to the additive errors. Our method is parsimonious compared to Bayesian nonparametric techniques based on Dirichlet process mixtures, flexible and general. Simulations based on synthetic time series are presented.
Parladé, Meaghan V.; Iverson, Jana M.
2012-01-01
From a dynamic systems perspective, transition points in development are times of increased instability, during which behavioral patterns are susceptible to temporary decoupling. This study investigated the impact of the vocabulary spurt on existing patterns of communicative coordination. Eighteen typically developing infants were videotaped at home 1 month before, at, and after the vocabulary spurt. Infants were identified as spurters if they underwent a discrete phase transition in vocabulary development (marked by an inflection point), and compared with a group of nonspurters whose word-learning rates followed a trajectory of continuous change. Relative to surrounding sessions, there were significant reductions in overall coordination of communicative behaviors and in words produced in coordination at the vocabulary spurt session for infants who experienced more dramatic vocabulary growth. In contrast, nonspurters demonstrated little change across sessions. Findings underscore the importance of transitions as opportunities for observing processes of developmental change. PMID:21219063
Parladé, Meaghan V; Iverson, Jana M
2011-05-01
From a dynamic systems perspective, transition points in development are times of increased instability, during which behavioral patterns are susceptible to temporary decoupling. This study investigated the impact of the vocabulary spurt on existing patterns of communicative coordination. Eighteen typically developing infants were videotaped at home 1 month before, at, and after the vocabulary spurt. Infants were identified as spurters if they underwent a discrete phase transition in vocabulary development (marked by an inflection point), and compared with a group of nonspurters whose word-learning rates followed a trajectory of continuous change. Relative to surrounding sessions, there were significant reductions in overall coordination of communicative behaviors and in words produced in coordination at the vocabulary spurt session for infants who experienced more dramatic vocabulary growth. In contrast, nonspurters demonstrated little change across sessions. Findings underscore the importance of transitions as opportunities for observing processes of developmental change.
Dynamic response of mechanical systems to impulse process stochastic excitations: Markov approach
NASA Astrophysics Data System (ADS)
Iwankiewicz, R.
2016-05-01
Methods for determination of the response of mechanical dynamic systems to Poisson and non-Poisson impulse process stochastic excitations are presented. Stochastic differential and integro-differential equations of motion are introduced. For systems driven by Poisson impulse process the tools of the theory of non-diffusive Markov processes are used. These are: the generalized Itô’s differential rule which allows to derive the differential equations for response moments and the forward integro-differential Chapman-Kolmogorov equation from which the equation governing the probability density of the response is obtained. The relation of Poisson impulse process problems to the theory of diffusive Markov processes is given. For systems driven by a class of non-Poisson (Erlang renewal) impulse processes an exact conversion of the original non-Markov problem into a Markov one is based on the appended Markov chain corresponding to the introduced auxiliary pure jump stochastic process. The derivation of the set of integro-differential equations for response probability density and also a moment equations technique are based on the forward integro-differential Chapman-Kolmogorov equation. An illustrating numerical example is also included.
NASA Astrophysics Data System (ADS)
Shit, Anindita; Chattopadhyay, Sudip; Chaudhuri, Jyotipratim Ray
2012-06-01
We arrive at the escape rate from a metastable state for a system of Brownian particles driven periodically by a space dependent, rapidly oscillating external perturbation (with frequency ω) in one dimension (one of the most important class of nonequilibrium system). Though the problem may seem to be time-dependent, and is poised on the extreme opposite side of adiabaticity, there exists a multiple scale perturbation theory ("Kapitza window") by means of which the dynamics can be treated in terms of an effective time-independent potential that is derived as an expansion in orders of 1/ω to the order ω-3. The resulting time-independent equation is then used to calculate the escape rate of physical systems from a metastable state induced by external monochromatic field in the moderate-to-large damping limit and to investigate the effect of ω on the resulting rate in conjunction with the thermal energy. With large value of ω, we find that the environment with moderate-to-large damping impedes the escape process of the particle while high amplitude of the periodic driving force allows the particle to cross the barrier with a large escape rate. A comparison of our theoretical expression with numerical simulation gives a satisfactory agreement.
USDA-ARS?s Scientific Manuscript database
Cropping systems over the past century have developed greater crop specialization, more effectively conserve our soil and water resources, and are more resilient. The purpose of this chapter is to discuss the evolution of cropping systems in the Northern Great Plains and provide an approach to crop...
Reaction dynamics of the D+ + H2 system. A comparison of theoretical approaches.
Jambrina, P G; Alvariño, J M; Aoiz, F J; Herrero, Víctor J; Sáez-Rábanos, Vicente
2010-10-21
The dynamics of the deuteron-proton exchange D(+) + H(2) → HD + H(+) reaction on its ground 1(1)A' potential energy surface has been the subject of a theoretical study for collision energies below 1.5 eV. The results obtained with three theoretical approaches: quasi-classical trajectory (QCT), statistical quasi-classical trajectory (SQCT), and accurate time-independent quantum mechanical (QM) calculations are compared in the range of collision energies from 5 meV to 0.2 eV. The QM calculations included all total angular momentum quantum numbers, J, up to J(max) ≈ 40 and all the Coriolis couplings. For higher collision energies, the comparison was restricted to the QCT and SQCT results given the enormous computational cost implied in the QM calculations. Reaction cross sections as a function of collision energy (excitation functions) for various initial rovibrational states have been determined and compared with the corresponding results for the endothermic H(+) + D(2) → HD + D(+) isotopic variant. The excitation function for the title reaction decays monotonically with collision energy as expected for an exothermic reaction without a barrier, in contrast to the behaviour observed in the mentioned H(+) + D(2) (v = 0, j ≤ 3). Reaction probabilities as a function of J (opacity functions) at several collision energies calculated with the different approaches were also examined and important differences between them were found. The effect of using the gaussian binning procedure that preserves, to a large extent, the zero point energy, as compared to the standard histogram binning in the QCT calculations, is also examined. At low collision energy, the best agreement with the accurate QM results is given by the SQCT data, although they tend to overestimate the reactivity. The deviations from the statistical behaviour of the QCT data at higher energies are remarkable. Nevertheless, on the whole, the title reaction can be deemed more statistical than the H(+) + D(2
NASA Astrophysics Data System (ADS)
Gromek, Katherine Emily
A novel computational and inference framework of the physics-of-failure (PoF) reliability modeling for complex dynamic systems has been established in this research. The PoF-based reliability models are used to perform a real time simulation of system failure processes, so that the system level reliability modeling would constitute inferences from checking the status of component level reliability at any given time. The "agent autonomy" concept is applied as a solution method for the system-level probabilistic PoF-based (i.e. PPoF-based) modeling. This concept originated from artificial intelligence (AI) as a leading intelligent computational inference in modeling of multi agents systems (MAS). The concept of agent autonomy in the context of reliability modeling was first proposed by M. Azarkhail [1], where a fundamentally new idea of system representation by autonomous intelligent agents for the purpose of reliability modeling was introduced. Contribution of the current work lies in the further development of the agent anatomy concept, particularly the refined agent classification within the scope of the PoF-based system reliability modeling, new approaches to the learning and the autonomy properties of the intelligent agents, and modeling interacting failure mechanisms within the dynamic engineering system. The autonomous property of intelligent agents is defined as agent's ability to self-activate, deactivate or completely redefine their role in the analysis. This property of agents and the ability to model interacting failure mechanisms of the system elements makes the agent autonomy fundamentally different from all existing methods of probabilistic PoF-based reliability modeling. 1. Azarkhail, M., "Agent Autonomy Approach to Physics-Based Reliability Modeling of Structures and Mechanical Systems", PhD thesis, University of Maryland, College Park, 2007.
Time-dependent analytical R-matrix approach for strong-field dynamics. I. One-electron systems
NASA Astrophysics Data System (ADS)
Torlina, Lisa; Smirnova, Olga
2012-10-01
We develop a flexible analytical approach to describe strong-field dynamics in atoms and molecules. The approach is based on the ideas of the R-matrix method. Here, we illustrate and validate our approach by applying it to systems with one active electron bound by the Coulomb potential and benchmark our results against the standard theory of Perelomov, Popov, and Terent'ev [Sov. Phys. JETP0021-903710.1007/BF01132710 23, 924 (1966)]. We discuss corrections to the ionization amplitude associated with the interplay of the Coulomb potential and the laser field on the sub-laser cycle time scale and the shape of the tunneling wave packets associated with different instants of ionization.
Phenomenological approach to describe oscillatory growth or decay in different dynamical systems
NASA Astrophysics Data System (ADS)
Biswas, Dibyendu; Poria, Swarup; Patra, Sankar Narayan
2016-12-01
The approach of the phenomenological universalities of growth is considered to describe the behaviour of a system showing an oscillatory growth. Two phenomenological classes are proposed to consider the oscillatory behaviour of a system. One of them is showing oscillatory nature with constant amplitude and the other represents oscillatory nature with a change in amplitude. The term responsible for decay (or growth) in amplitude in the proposed class is also been identified. The variations in the nature of oscillation with the dependent parameters are studied in this communication. In this connection, the variation of a specific growth rate is also been considered. The significance of the presence and the absence of each term involved in the phenomenological description are also taken into consideration. These proposed classes might be useful for the experimentalists to extract a characteristic feature from the data set and to develop a suitable model consistent with their data set.
An Improved Incremental Learning Approach for KPI Prognosis of Dynamic Fuel Cell System.
Yin, Shen; Xie, Xiaochen; Lam, James; Cheung, Kie Chung; Gao, Huijun
2016-12-01
The key performance indicator (KPI) has an important practical value with respect to the product quality and economic benefits for modern industry. To cope with the KPI prognosis issue under nonlinear conditions, this paper presents an improved incremental learning approach based on available process measurements. The proposed approach takes advantage of the algorithm overlapping of locally weighted projection regression (LWPR) and partial least squares (PLS), implementing the PLS-based prognosis in each locally linear model produced by the incremental learning process of LWPR. The global prognosis results including KPI prediction and process monitoring are obtained from the corresponding normalized weighted means of all the local models. The statistical indicators for prognosis are enhanced as well by the design of novel KPI-related and KPI-unrelated statistics with suitable control limits for non-Gaussian data. For application-oriented purpose, the process measurements from real datasets of a proton exchange membrane fuel cell system are employed to demonstrate the effectiveness of KPI prognosis. The proposed approach is finally extended to a long-term voltage prediction for potential reference of further fuel cell applications.
Keliris, Christodoulos; Polycarpou, Marios M; Parisini, Thomas
2017-04-01
This paper develops an integrated filtering and adaptive approximation-based approach for fault diagnosis of process and sensor faults in a class of continuous-time nonlinear systems with modeling uncertainties and measurement noise. The proposed approach integrates learning with filtering techniques to derive tight detection thresholds, which is accomplished in two ways: 1) by learning the modeling uncertainty through adaptive approximation methods and 2) by using filtering for dampening measurement noise. Upon the detection of a fault, two estimation models, one for process and the other for sensor faults, are initiated in order to identify the type of fault. Each estimation model utilizes learning to estimate the potential fault that has occurred, and adaptive isolation thresholds for each estimation model are designed. The fault type is deduced based on an exclusion-based logic, and fault detectability and identification conditions are rigorously derived, characterizing quantitatively the class of faults that can be detected and identified by the proposed scheme. Finally, simulation results are used to demonstrate the effectiveness of the proposed approach.
Shkvarko, Yuriy; Tuxpan, José; Santos, Stewart
2011-01-01
We consider a problem of high-resolution array radar/SAR imaging formalized in terms of a nonlinear ill-posed inverse problem of nonparametric estimation of the power spatial spectrum pattern (SSP) of the random wavefield scattered from a remotely sensed scene observed through a kernel signal formation operator and contaminated with random Gaussian noise. First, the Sobolev-type solution space is constructed to specify the class of consistent kernel SSP estimators with the reproducing kernel structures adapted to the metrics in such the solution space. Next, the “model-free” variational analysis (VA)-based image enhancement approach and the “model-based” descriptive experiment design (DEED) regularization paradigm are unified into a new dynamic experiment design (DYED) regularization framework. Application of the proposed DYED framework to the adaptive array radar/SAR imaging problem leads to a class of two-level (DEED-VA) regularized SSP reconstruction techniques that aggregate the kernel adaptive anisotropic windowing with the projections onto convex sets to enforce the consistency and robustness of the overall iterative SSP estimators. We also show how the proposed DYED regularization method may be considered as a generalization of the MVDR, APES and other high-resolution nonparametric adaptive radar sensing techniques. A family of the DYED-related algorithms is constructed and their effectiveness is finally illustrated via numerical simulations. PMID:22163859
Shkvarko, Yuriy; Tuxpan, José; Santos, Stewart
2011-01-01
We consider a problem of high-resolution array radar/SAR imaging formalized in terms of a nonlinear ill-posed inverse problem of nonparametric estimation of the power spatial spectrum pattern (SSP) of the random wavefield scattered from a remotely sensed scene observed through a kernel signal formation operator and contaminated with random Gaussian noise. First, the Sobolev-type solution space is constructed to specify the class of consistent kernel SSP estimators with the reproducing kernel structures adapted to the metrics in such the solution space. Next, the "model-free" variational analysis (VA)-based image enhancement approach and the "model-based" descriptive experiment design (DEED) regularization paradigm are unified into a new dynamic experiment design (DYED) regularization framework. Application of the proposed DYED framework to the adaptive array radar/SAR imaging problem leads to a class of two-level (DEED-VA) regularized SSP reconstruction techniques that aggregate the kernel adaptive anisotropic windowing with the projections onto convex sets to enforce the consistency and robustness of the overall iterative SSP estimators. We also show how the proposed DYED regularization method may be considered as a generalization of the MVDR, APES and other high-resolution nonparametric adaptive radar sensing techniques. A family of the DYED-related algorithms is constructed and their effectiveness is finally illustrated via numerical simulations.
Lukic, Luka; Santos-Victor, José; Billard, Aude
2014-04-01
We investigate the role of obstacle avoidance in visually guided reaching and grasping movements. We report on a human study in which subjects performed prehensile motion with obstacle avoidance where the position of the obstacle was systematically varied across trials. These experiments suggest that reaching with obstacle avoidance is organized in a sequential manner, where the obstacle acts as an intermediary target. Furthermore, we demonstrate that the notion of workspace travelled by the hand is embedded explicitly in a forward planning scheme, which is actively involved in detecting obstacles on the way when performing reaching. We find that the gaze proactively coordinates the pattern of eye-arm motion during obstacle avoidance. This study provides also a quantitative assessment of the coupling between the eye-arm-hand motion. We show that the coupling follows regular phase dependencies and is unaltered during obstacle avoidance. These observations provide a basis for the design of a computational model. Our controller extends the coupled dynamical systems framework and provides fast and synchronous control of the eyes, the arm and the hand within a single and compact framework, mimicking similar control system found in humans. We validate our model for visuomotor control of a humanoid robot.
Quantifying a strategic view of diabetes technology impacts: a system dynamics approach.
Edwards, Roger A; Graham, Alan; Williams, Melissa; Amati, Mike; Wright, Caroline; Lee, Mei; Walsh, Dan; Hughes, Nick
2009-07-01
Diabetes and its related complications and comorbidities (C&Cs) represent a significant and increasing healthcare burden. Absence of a systematic manner to evaluate value propositions of technologies from various stakeholders' perspectives impedes the best uses of current and emerging technologies. A system dynamics methodology was used to develop a comprehensive causal simulator of the U.S. population and give proof of principle that entire portfolios of present and future technologies can be evaluated for direct and indirect impacts. An explicit semiquantitative methodology was used for surveying, prioritizing, and grouping C&Cs, patient subgroups, and technologies, utilizing diverse publicly available clinical literature. The resulting model simulates the incidence and prevalence of diabetes and 10 of its most commonly associated C&Cs, reflecting their interrelated upstream and downstream relationships. The simulator enables systematic evaluation of tens of thousands of potential combinations of emerging technologies and technology leverage points that can be used to improve patient outcomes and guide technology investments. Feasibility was demonstrated through single, pair-wise, and targeted analyses of technologies. This effort demonstrated the feasibility of linking complex, interconnected disease states, impact points, outcomes, and interventions with a variety of outcome metrics, to an extent greater than existing models developed for other purposes. The project demonstrated the ability to identify priority technologies and pipeline therapies and leverage points among diabetes interventions. It demonstrated more effective knowledge management of diverse information essential for formulating strategy that could be applied in a wide range of therapeutic applications and technology innovation uses.
Analysis of liquid natural gas as a truck fuel: a system dynamics approach
Bray, M.A.; Sebo, D.E.; Mason, T.L.; Mills, J.I.; Rice, R.E.
1996-10-01
The purpose of this analysis is to evaluate the potential for growth in use of liquid natural gas (LNG) fueled trucks. . A system dynamics model was constructed for the analysis and a variety of scenarios were investigated. The analysis considers the economics of LNG fuel in the context of the trucking industry to identify barriers to the increased use of LNG trucks and potential interventions or leverage points which may overcome these barriers. The study showed that today, LNG use in trucks is not yet economically viable. A large change in the savings from fuel cost or capital cost is needed for the technology to take off. Fleet owners have no way now to benefit from the environmental benefits of LNG fuel nor do they benefit from the clean burning nature of the fuel. Changes in the fuel cost differential between diesel and LNG are not a research issue. However, quantifying the improvements in reliability and wear from the use of clean fuel could support increased maintenance and warranty periods. Many people involved in the use of LNG for trucks believe that LNG has the potential to occupy a niche within the larger diesel truck business. But if LNG in trucks can become economic, the spread of fuel stations and technology improvements could lead to LNG trucks becoming the dominant technology. An assumption in our simulation work is that LNG trucks will be purchased when economically attractive. None of the simulation results show LNG becoming economic but then only to the level of a niche market.
Dynamics of Zn in an urban wetland soil-plant system: Coupling isotopic and EXAFS approaches
NASA Astrophysics Data System (ADS)
Aucour, Anne-Marie; Bedell, Jean-Philippe; Queyron, Marine; Magnin, Valérie; Testemale, Denis; Sarret, Géraldine
2015-07-01
Plants play a key role in the stabilization of metals in contaminated environments. Studies have been performed on Zn uptake and storage mechanisms, mainly for Zn hyperaccumulating plants, though less is known about Zn stabilization in the rhizosphere of non-accumulating plants. This study was focused on the dynamics of Zn in a whole soil-litter-plant system and the processes controlling Zn mobilization and stabilization. The site studied was an infiltration basin receiving urban stormwater, in which Phalaris arundinacea (reed canary grass) developed spontaneously. A combination of chemical extractions (CaCl2, DTPA), EXAFS spectroscopy and Zn stable isotope measurements was applied for the water inlet, soil, plant organs and decaying biomass. Zn speciation changed from the water inlet to the soil. In the soil, Zn was present as Zn-layered double hydroxide (Zn-LDH), tetrahedral and octahedral sorbed Zn species. The formation of Zn-LDH participates in Zn stabilization. Tetrahedral Zn species, which were partly DTPA exchangeable, were enriched in heavy isotopes, whereas octahedral Zn (Zn-LDH and sorbed species) were enriched in light isotopes. Based on a linear model between δ66Zn and Zn speciation, δ66Zn for pure tetrahedral and octahedral end-members were estimated at ca. 0.33‰ and 0.04‰, respectively. In the plant, a mixture of octahedral Zn (attributed to aqueous Zn-organic acid complexes present in the symplasm), and tetrahedral Zn (attributed to apoplasmic Zn-cell wall complexes) was observed in all organs. Large enrichment in light isotopes from the soil to the plant Δ66Zn (of ca. -0.6‰) was observed. The stem was enriched in light isotopes versus roots and, to a lesser extent, versus leaves. The results suggest that Zn was taken up via a low-affinity transport system and that Zn was sequestrated in the stem symplasm after transit through leaves. Finally, intense Zn exchanges were observed between the decaying biomass and the soil, with the sorption of
Rural poverty and environmental degradation in the Philippines: A system dynamics approach
NASA Astrophysics Data System (ADS)
Parayno, Phares Penuliar
Poverty among the small cultivators in the Philippines remains widespread despite a general increase in per capita income during the last three decades. At the same time, the degradation of agricultural land resources, as sources of daily subsistence for the rural workers, is progressing. Past policy studies on the alleviation of rural poverty in the developing countries have centered on the issue of increasing food production and expanding economic growth but gave little attention to the issue of constraints imposed by degradation of agricultural land resources. Only in recent years have there been increasing focus on the relationship between rural poverty and environmental degradation. Inquiry is, however, often done by simplistic one way causal relationships which, although often illuminating, does not provide a comprehensive understanding of the different interacting processes that create rural poverty and land degradation. Thus, policies ensuing from such analyses provide only short-term gains without effecting lasting improvement in the living conditions of the small cultivators. This dissertation examines the complex interrelationships between rural poverty and land degradation and attempts to explain the inefficacy of broad development programs implemented in alleviating rural poverty and reversing deterioration of land resources. The study uses the case of the Philippines for empirical validation. The analysis employs computer simulation experiments with a system dynamics model of a developing economy consisting of an agricultural sector whose microstructure incorporates processes influencing: agricultural production; disbursement of income; changes in the quality of agricultural land resources; demographic behavior; and rural-urban transfer of real and monetary resources. The system dynamics model used in this study extends the wage and income distribution model of Saeed (1988) by adding to it decision structures concerning changes in the quality of
Indonesian CPO availability analysis to support food and energy security: a system dynamic approach
NASA Astrophysics Data System (ADS)
Rahman, T.; Arkeman, Y.; Setyaningsih, D.; Saparita, R.
2017-05-01
The development of biofuels could be a solution to overcome the energy problem. One of biofuel that has the potential to be developed, namely palm oil biodiesel that is also the raw material for food. As a provider of CPO raw materials, the production of palm biodiesel could trigger competitions, from biofuels demand growth and utilization of agricultural resources. Thus, it needs to be analyzed to determine the adequency of CPO supply to fulfill the need of food and policy recomendation which sets the development of palm oil biodiesel can be synergies with food need especially for the supply of raw material CPO. To obtain the optimal policy in the synergy between the raw material of CPO for food and energy is a need to establish some policy scenarios that allow to be applied and then chosen the best policy alternative of all scenarios. The purpose of this research were to : 1) analysis the availability of CPO to meet the needs of food and energy, 2) provide policy recommendation with regard biodiesel development of food security. The model made used system dynamic method. Several scenarios that used in the model are: 1) existing condition, 2) The scenario increase biodiesel production capacity and increase land productivity, 3) reduction scenario CPO export by 30%, 4) scenario use othe raw material for biodiesel by 20%. The simulation results showed the availability of CPO raw materials would answer all needs of both food and biodiesel when there was an increase in productivity, diversification of raw materials, and also a reduction in palm oil exports. It was needed an integrated policy from upstream to downstream along with the consistency of implementation. Policy suggestions that could be considered were increased productivity through agricultural intensification, enforcement disincentive policies of CPO to exports, and development of non-CPO biodiesel raw materials and development of renewable energy.
Wang, Aixing; Fang, Chao; Liu, Yibao
2017-01-07
In this article the dynamic features of the highly excited vibrational states of the hypochlorous acid (HOCl) non-integrable system are studied using the dynamic potential and Lyapunov exponent approaches. On the condition that the 3:1 resonance between the H-O stretching and H-O-Cl bending modes accompany the 2:1 Fermi resonance between the O-Cl stretching and H-O-Cl bending modes, it is found that the dynamic potentials of the highly excited vibrational states vary regularly with different Polyad numbers (P numbers). As the P number increases, the dynamic potentials of the H-O stretching mode remain the same, but those of the H-O-Cl bending mode gradually become complex. In order to investigate the chaotic and stable features of the highly excited vibrational states of the HOCl non-integrable system, the Lyapunov exponents of different energy levels lying in the dynamic potentials of the H-O-Cl bending mode (P = 4 and 5) are calculated. It is shown that the Lyapunov exponents of the energy levels staying in the junction of Morse potential and inverse Morse potential are relative large, which indicates the degrees of chaos for these energy levels is relatively high, but the stabilities of the corresponding states are good. These results could be interpreted as the intramolecular vibrational relaxation (IVR) acting strongly via the HOCl bending motion and causing energy transfers among different modes. Based on the previous studies, these conclusions seem to be generally valid to some extent for non-integrable triatomic molecules.
NASA Astrophysics Data System (ADS)
Ivancevic, Vladimir G.; Ivancevic, Tijana T.
The main objective is to show that high-dimensional nonlinear systems in "real life" can be modeled and analyzed using rigorous mathematics, which enables their complete predictability and controllability, as if they were linear systems.
Hill, Andrew; Camacho, Oscar M
2017-03-22
In 2012 the US FDA suggested the use of mathematical models to assess the impact of releasing new nicotine or tobacco products on population health outcomes. A model based on system dynamics methodology was developed to project the potential effects of a new nicotine product at a population level. A model representing traditional smoking populations (never, current and former smokers) and calibrated using historical data was extended to a two-product model by including electronic cigarettes use statuses. Smoking mechanisms, such as product initiation, switching, transition to dual use, and cessation, were represented as flows between smoking statuses (stocks) and the potential effect of smoking renormalisation through a feedback system. Mortality over a 50-year period (2000-2050) was the health outcome of interest, and was compared between two scenarios, with and without e-cigarettes being introduced. The results suggest that by 2050, smoking prevalence in adults was 12.4% in the core model and 9.7% (including dual users) in the counterfactual. Smoking-related mortality was 8.4% and 8.1%, respectively. The results suggested an overall beneficial effect from launching e-cigarettes and that system dynamics could be a useful approach to assess the potential population health effects of nicotine products when epidemiological data are not available.
Lyon, Aaron R; Maras, Melissa A; Pate, Christina M; Igusa, Takeru; Vander Stoep, Ann
2016-03-01
Although it is widely known that the occurrence of depression increases over the course of adolescence, symptoms of mood disorders frequently go undetected. While schools are viable settings for conducting universal screening to systematically identify students in need of services for common health conditions, particularly those that adversely affect school performance, few school districts routinely screen their students for depression. Among the most commonly referenced barriers are concerns that the number of students identified may exceed schools' service delivery capacities, but few studies have evaluated this concern systematically. System dynamics (SD) modeling may prove a useful approach for answering questions of this sort. The goal of the current paper is therefore to demonstrate how SD modeling can be applied to inform implementation decisions in communities. In our demonstration, we used SD modeling to estimate the additional service demand generated by universal depression screening in a typical high school. We then simulated the effects of implementing "compensatory approaches" designed to address anticipated increases in service need through (1) the allocation of additional staff time and (2) improvements in the effectiveness of mental health interventions. Results support the ability of screening to facilitate more rapid entry into services and suggest that improving the effectiveness of mental health services for students with depression via the implementation of an evidence-based treatment protocol may have a limited impact on overall recovery rates and service availability. In our example, the SD approach proved useful in informing systems' decision-making about the adoption of a new school mental health service.
Jaén, Sebastian; Dyner, Isaac
2014-03-01
A large-scale expansion of the Colombian coca cultivation is one of the most revealing signs of a structural change in the illegal cocaine market in the Andean region. From being a modest and domestic production, in the space of five years Colombian coca cultivation supplied a competitive market, capable of substituting almost completely the foreign sources of supply. The purpose of this work is to explore the role and potential of system dynamics (SD) as a modeling methodology to better understand the consequences of drug policy. As a case study, this work tests the hypothesis that the outbreak of Colombian coca cultivations is a consequence of the take down of large cartels, leading to the surge of small drug-trafficking firms called "cartelitos." Using an SD model, and elements from the economic theory of the criminal firm, our work shows how the formation of these small firms might significantly contribute to the configuring of a more competitive domestic coca industry (and hence to a more efficient crime industry). We conclude that SD seems an appropriate dynamic modeling-based approach to address policy issues regarding drug markets. The methodology takes into account the dynamic nature of drug markets and their multi-dimensional responses to policy interventions. Copyright © 2014 Elsevier B.V. All rights reserved.
NASA Astrophysics Data System (ADS)
Le Couteulx, Alexis; Wolf, Cédric; Pérès, Guénola; Hallaire, Vincent
2015-04-01
In agriculture, one of the main purposes of innovative systems is to preserve and improve soil quality and noticeably their physical quality. This physical quality of a soil is intimately linked with its structure, i.e. the spatial arrangement of voids and solids. It is well-known that agricultural systems may deeply impact on soil structure through their effect on various structuring processes, in particular (i) the mechanical action of soil tillage and (ii) the burrowing activity and casts production of earthworms. As the assessment of agricultural systems needs long term experiments, it is not feasible to assess them all. However, the modeling approach has been used seldom despite it seems promising. As a first step towards the modeling of agricultural systems, we propose a model that simulates the impact of earthworm bioturbation and several tillage practices on soil structure dynamics. The proposed model accounts for two earthworm ecological categories: anecics and endogeics. Anecics are split into epi-anecics and true anecics and endogeics are kept at the specific level. The model takes into account their physiological and morphological features such as their diapause period, their gut transit time or their body size. In order to simulate the bioturbation activity of earthworms, they can make six different actions: (i) burrow new paths by ingesting soil particles, (ii) move inside existing paths, (iii) move to soil surface, (iv) wait, (v) produce a subsurface cast or (vi) produce a surface cast. For the various species and groups of earthworms, the probability of these actions was adjusted from experiments and published results. This part of the model dedicated to earthworms allows to build and study their network of burrows but also the position and volume of their subsurface and surface casts. This network may be couple with models of water conductivity to assess the role of earthworm on this soil functional property. To better simulate soil structure
NASA Astrophysics Data System (ADS)
Huentutripay, Jorge; Jazar, Mustapha; Véron, Laurent
We study the existence of singular separable solutions to the 2-dimensional quasilinear equation -∇·(|∇ u| p-2 ∇ u)+| u| q-1 u=0 under the form u( r, θ)= r- βω( θ). We obtain the full description of the set of such solutions by combining a 2-dimensional shooting method with a phase plane analysis approach.
A system dynamics approach to develop a recovery model in the Malaysian automotive industry
NASA Astrophysics Data System (ADS)
Mohamad-Ali, N.; Ghazilla, R. A. R.; Abdul-Rashid, S. H.; Sakundarini, N.; Ahmad-Yazid, A.; Stephenie, L.
2017-06-01
Design strategies play a significant role to enhance recovery effectiveness at the end of product life cycle. By reviewing previous study, there are many factors involved to enhance recovery effectiveness but limited to linking design strategies factors in holistic and dynamics view. Proposed method are explained and an initial model for end-of-life vehicles (ELVs) recovery model illustrated in graphical and numerical data is presented. However this is limited to authors understanding and preliminary data which requires collaboration between designers and other stakeholders to develop a model based on actual situation.
NASA Technical Reports Server (NTRS)
Nese, Jon M.
1989-01-01
A dynamical systems approach is used to quantify the instantaneous and time-averaged predictability of a low-order moist general circulation model. Specifically, the effects on predictability of incorporating an active ocean circulation, implementing annual solar forcing, and asynchronously coupling the ocean and atmosphere are evaluated. The predictability and structure of the model attractors is compared using the Lyapunov exponents, the local divergence rates, and the correlation, fractal, and Lyapunov dimensions. The Lyapunov exponents measure the average rate of growth of small perturbations on an attractor, while the local divergence rates quantify phase-spatial variations of predictability. These local rates are exploited to efficiently identify and distinguish subtle differences in predictability among attractors. In addition, the predictability of monthly averaged and yearly averaged states is investigated by using attractor reconstruction techniques.
NASA Astrophysics Data System (ADS)
Pioli, L.; Azzopardi, B. J.; Bonadonna, C.; Marchetti, E.; Ripepe, M.
2009-12-01
Open conduit basaltic volcanoes are characterized by frequent eruptions, usually consisting in mild Strombolian and Hawaiian explosions, alternating years to months of quiescence periods, with degassing activity from the central conduit. Recent improvements of thermal, video, radar and acoustic monitoring techniques have provided new powerful tools for the study of degassing processes and made available geophysical and geochemical datasets for many central volcanoes, such as Stromboli, Etna (Italy), Kilauea (Hawaii), Villarrica (Chile). These studies revealed that degassing is an unsteady, often pulsatory process, characterized by fluctuations in both intensity and composition of the emitted gases. Unambiguous interpretation of monitoring data of surface activity in terms of conduit dynamics and flow processes is, however, not possible, due to partial knowledge of the physical processes controlling the dynamics of two-phase flows in magmas. We performed a series of experiments to gain further insights on the dynamics of the gas-bubble rise in magmas within a cylindrical conduit, their ability to segregate and coalesce and the effect of these processes on the degassing dynamics. The experiments consisted in generating fluxes at variable intensities of air through stagnant water or glucose syrup in a bubble column apparatus 6.5 m high and with a diameter of 24 cm diameter. Glucose syrup and water are Newtonian liquids with viscosity ranging from 2.4 to 204.0 Pa*s and from 1.7 to 0.2 10 -3 Pa*s respectively, depending on temperature. Air was inserted at the base of the column through a variable number (1 to 25) of 5mm-diameter nozzles reaching surficial gas velocities of up to 0.5 m/s. The activity of the bubble column was monitored through temperature, pressure, void fraction and acoustic measurements and filmed by a high-speed camera with maximum resolution of 800x600 pixels. Pressure fluctuations, vesicularity and acoustic signal were then analyzed and correlated
A Dynamical Systems Approach to the Design of the Science Orbit Around Europa
NASA Technical Reports Server (NTRS)
Gomez, Gerard; Lara, Martin; Russell, Ryan P.
2006-01-01
The science orbit for a future mission to Europa requires low eccentricity, low altitude, and high inclination. However, high inclination orbits around planetary satellites are unstable due to third-body perturbations. Without control, the orbiter impacts Europa after few weeks. To minimize control, a tour over the stable-unstable, averaged manifolds of unstable frozen orbits has been suggested. We proceed with the unaveraged equations and study the manifolds of unstable orbits that are periodic in a rotating frame attached to Europa. Massive numerical computation helps in understanding the unstable dynamics close to Europa, and, thus, in selecting long lifetime high inclination orbits. A final test of a selected set of initial conditions on a high fidelity, ephemeris model, validate the results.
A Dynamical Systems Approach to the Design of the Science Orbit Around Europa
NASA Technical Reports Server (NTRS)
Gomez, Gerard; Lara, Martin; Russell, Ryan P.
2006-01-01
The science orbit for a future mission to Europa requires low eccentricity, low altitude, and high inclination. However, high inclination orbits around planetary satellites are unstable due to third-body perturbations. Without control, the orbiter impacts Europa after few weeks. To minimize control, a tour over the stable-unstable, averaged manifolds of unstable frozen orbits has been suggested. We proceed with the unaveraged equations and study the manifolds of unstable orbits that are periodic in a rotating frame attached to Europa. Massive numerical computation helps in understanding the unstable dynamics close to Europa, and, thus, in selecting long lifetime high inclination orbits. A final test of a selected set of initial conditions on a high fidelity, ephemeris model, validate the results.
NASA Technical Reports Server (NTRS)
Ider, Sitki Kemal
1989-01-01
Conventionally kinematical constraints in multibody systems are treated similar to geometrical constraints and are modeled by constraint reaction forces which are perpendicular to constraint surfaces. However, in reality, one may want to achieve the desired kinematical conditions by control forces having different directions in relation to the constraint surfaces. The conventional equations of motion for multibody systems subject to kinematical constraints are generalized by introducing general direction control forces. Conditions for the selections of the control force directions are also discussed. A redundant robotic system subject to prescribed end-effector motion is analyzed to illustrate the methods proposed.
NASA Astrophysics Data System (ADS)
García-Garrido, V. J.; Mancho, A. M.; Wiggins, S.; Mendoza, C.
2015-11-01
The disappearance of Malaysia Airlines flight MH370 on the morning of 8 March 2014 is one of the great mysteries of our time. Perhaps the most relevant aspect of this mystery is that not a single piece of debris from the aircraft was found during the intensive surface search carried out for roughly 2 months following the crash. Difficulties in the search efforts, due to the uncertainty of the plane's final impact point and the time that had passed since the accident, bring the question on how the debris scattered in an always moving ocean, for which there are multiple data sets that do not uniquely determine its state. Our approach to this problem is based on the use of Lagrangian descriptors (LD), a novel mathematical tool coming from dynamical systems theory that identifies dynamic barriers and coherent structures governing transport. By combining publicly available information supplied by different ocean data sources with these mathematical techniques, we are able to assess the spatio-temporal state of the ocean in the priority search area at the time of impact and the following weeks. Using this information we propose a revised search strategy by showing why one might not have expected to find debris in some large search areas targeted by the Australian Maritime Safety Authority (AMSA), and determining regions where one might have expected impact debris to be located, which were not subjected to any exploration.
Dynamic State Estimation of Power Systems With Quantization Effects: A Recursive Filter Approach.
Hu, Liang; Wang, Zidong; Liu, Xiaohui
2016-08-01
In this paper, a recursive filter algorithm is developed to deal with the state estimation problem for power systems with quantized nonlinear measurements. The measurements from both the remote terminal units and the phasor measurement unit are subject to quantizations described by a logarithmic quantizer. Attention is focused on the design of a recursive filter such that, in the simultaneous presence of nonlinear measurements and quantization effects, an upper bound for the estimation error covariance is guaranteed and subsequently minimized. Instead of using the traditional approximation methods in nonlinear estimation that simply ignore the linearization errors, we treat both the linearization and quantization errors as norm-bounded uncertainties in the algorithm development so as to improve the performance of the estimator. For the power system with such kind of introduced uncertainties, a filter is designed in the framework of robust recursive estimation, and the developed filter algorithm is tested on the IEEE benchmark power system to demonstrate its effectiveness.
MODELING AIR FLOW DYNAMICS IN RADON MITIGATION SYSTEMS: A SIMPLIFIED APPROACH
The paper refines and extends an earlier study--relating to the design of optimal radon mitigation systems based on subslab depressurization-- that suggested that subslab air flow induced by a central suction point be treated as radial air flow through a porous bed contained betw...
MODELING AIR FLOW DYNAMICS IN RADON MITIGATION SYSTEMS: A SIMPLIFIED APPROACH
The paper refines and extends an earlier study--relating to the design of optimal radon mitigation systems based on subslab depressurization-- that suggested that subslab air flow induced by a central suction point be treated as radial air flow through a porous bed contained betw...
2010-03-01
2001. An Introduction to Systems Thinking. Lebanon, NH: HPS Inc. Jeanneret, P. Richard and Strong, Mark H. 2003. “Linking O*NET job analysis ...information to job requirement predictors: An O*NET application.” Personnel Psychology. 56(2), 465-492. Katzer, Dee Jay. 2002. " Decision analysis ...35 vii Page IV. Analysis and Results
Remaud, Anthony; Cornu, Christophe; Guével, Arnaud
2005-01-01
Context: Although isotonic and isokinetic exercises are commonly used in sports medicine and rehabilitation, studies comparing their effects on the neuromuscular system have provided conflicting results. Objective: To compare responses of the neuromuscular system to isotonic and isokinetic contractions by controlling the total external amount of work performed and the mean angular movement velocity. Design: A familiarization session was followed by isotonic and isokinetic sessions of tests performed on an isokinetic dynamometer. Each subject participated in 3 sessions. Setting: A sport sciences research laboratory. Patients or Other Participants: Nine healthy adult males with no history of knee injury. Intervention(s): The isotonic session consisted of 3 sets of 8 knee extensions at 80% of each subject's maximal voluntary isotonic contraction. The isokinetic session involved 3 sets of n knee extensions at a preset velocity equivalent to the mean velocity measured during the corresponding isotonic sets; n represented the number of repetitions subjects had to achieve to equalize the total external amount of work performed during the corresponding isotonic sets. Main Outcome Measure(s): We recorded mechanical parameters, n, and surface electromyographic signals from the vastus medialis, rectus femoris, and vastus lateralis muscles. Then root mean square, mean power frequency, and neuromuscular efficiency values were calculated for each repetition. Results: As expected, the total external amount of work and mean angular velocity were similar between the isotonic and isokinetic sessions. The number of repetitions performed was equivalent in both sessions. In addition, although no “shift” of mean power frequency occurred, mean neuromuscular efficiency decreased linearly with repetitions for both modes in no differentiated way. Conclusions: Standardization of isotonic and isokinetic contractions based on total external amount of work and movement velocity is possible
Takeuchi, Nobuto; Hogeweg, Paulien
2012-09-01
We review computational studies on prebiotic evolution, focusing on informatic processes in RNA-like replicator systems. In particular, we consider the following processes: the maintenance of information by replicators with and without interactions, the acquisition of information by replicators having a complex genotype-phenotype map, the generation of information by replicators having a complex genotype-phenotype-interaction map, and the storage of information by replicators serving as dedicated templates. Focusing on these informatic aspects, we review studies on quasi-species, error threshold, RNA-folding genotype-phenotype map, hypercycle, multilevel selection (including spatial self-organization, classical group selection, and compartmentalization), and the origin of DNA-like replicators. In conclusion, we pose a future question for theoretical studies on the origin of life.
Takeuchi, Nobuto; Hogeweg, Paulien
2012-01-01
We review computational studies on prebiotic evolution, focusing on informatic processes in RNA-like replicator systems. In particular, we consider the following processes: the maintenance of information by replicators with and without interactions, the acquisition of information by replicators having a complex genotype-phenotype map, the generation of information by replicators having a complex genotype-phenotype-interaction map, and the storage of information by replicators serving as dedicated templates. Focusing on these informatic aspects, we review studies on quasi-species, error threshold, RNA-folding genotype-phenotype map, hypercycle, multilevel selection (including spatial self-organization, classical group selection, and compartmentalization), and the origin of DNA-like replicators. In conclusion, we pose a future question for theoretical studies on the origin of life. PMID:22727399
Leondes, C.T. . Dept. of Electrical Engineering)
1991-01-01
This volume covers topics related to analysis and control system techniques for electric power systems. Topics include: simulation of multimachine power system dynamics, computer simulation in electric distribution systems, transient stability assessment, dynamic stability analysis, and improved power system control techniques.
Leondes, C.T. . Dept. of Electrical Engineering)
1991-01-01
This volume contains papers on analysis and control system techniques for electric power systems. Topics include: modeling and control of electric power systems, dynamic state estimation techniques, optimal power flow algorithms, and neural networks in power systems.
NASA Astrophysics Data System (ADS)
Ochoa, C. G.; Tidwell, V. C.
2012-12-01
In the arid southwestern United States community water management systems have adapted to cope with climate variability and with socio-cultural and economic changes that have occurred since the establishment of these systems more than 300 years ago. In New Mexico, the community-based irrigation systems were established by Spanish settlers and have endured climate variability in the form of low levels of precipitation and have prevailed over important socio-political changes including the transfer of territory between Spain and Mexico, and between Mexico and the United States. Because of their inherent nature of integrating land and water use with society involvement these community-based systems have multiple and complex economic, ecological, and cultural interactions. Current urban population growth and more variable climate conditions are adding pressure to the survival of these systems. We are conducting a multi-disciplinary research project that focuses on characterizing these intrinsically complex human and natural interactions in three community-based irrigation systems in northern New Mexico. We are using a system dynamics approach to integrate different hydrological, ecological, socio-cultural and economic aspects of these three irrigation systems. Coupled with intensive field data collection, we are building a system dynamics model that will enable us to simulate important linkages and interactions between environmental and human elements occurring in each of these water management systems. We will test different climate variability and population growth scenarios and the expectation is that we will be able to identify critical tipping points of these systems. Results from this model can be used to inform policy recommendations relevant to the environment and to urban and agricultural land use planning in the arid southwestern United States.
Dynamic Interactive Learning Systems
ERIC Educational Resources Information Center
Sabry, Khaled; Barker, Jeff
2009-01-01
This paper reviews and discusses the notions of interactivity and dynamicity of learning systems in relation to information technologies and design principles that can contribute to interactive and dynamic learning. It explores the concept of dynamic interactive learning systems based on the emerging generation of information as part of a…
Gessner, Manuel; Breuer, Heinz-Peter
2013-04-01
We obtain exact analytic expressions for a class of functions expressed as integrals over the Haar measure of the unitary group in d dimensions. Based on these general mathematical results, we investigate generic dynamical properties of complex open quantum systems, employing arguments from ensemble theory. We further generalize these results to arbitrary eigenvalue distributions, allowing a detailed comparison of typical regular and chaotic systems with the help of concepts from random matrix theory. To illustrate the physical relevance and the general applicability of our results we present a series of examples related to the fields of open quantum systems and nonequilibrium quantum thermodynamics. These include the effect of initial correlations, the average quantum dynamical maps, the generic dynamics of system-environment pure state entanglement and, finally, the equilibration of generic open and closed quantum systems.
Creative dynamics approach to neural intelligence.
Zak, M
1990-01-01
The thrust of this paper is to introduce and discuss a substantially new type of dynamical system for modelling biological behavior. The approach was motivated by an attempt to remove one of the most fundamental limitations of artificial neural networks-their rigid behavior compared with even simplest biological systems. This approach exploits a novel paradigm in nonlinear dynamics based upon the concept of terminal attractors and repellers. It was demonstrated that non-Lipschitzian dynamics based upon the failure of Lipschitz condition exhibits a new qualitative effect--a multi-choice response to periodic external excitations. Based upon this property, a substantially new class of dynamical systems--the unpredictable systems--was introduced and analyzed. These systems are represented in the form of coupled activation and learning dynamical equations whose ability to be spontaneously activated is based upon two pathological characteristics. Firstly, such systems have zero Jacobian. As a result of that, they have an infinite number of equilibrium points which occupy curves, surfaces or hypersurfaces. Secondly, at all these equilibrium points, the Lipschitz conditions fails, so the equilibrium points become terminal attractors or repellers depending upon the sign of the periodic excitation. Both of these pathological characteristics result in multi-choice response of unpredictable dynamical systems. It has been shown that the unpredictable systems can be controlled by sign strings which uniquely define the system behaviors by specifying the direction of the motions in the critical points. By changing the combinations of signs in the code strings the system can reproduce any prescribed behavior to a prescribed accuracy.(ABSTRACT TRUNCATED AT 250 WORDS)
NASA Astrophysics Data System (ADS)
Villarreal, Miguel L.
Riparian systems are comprised of interacting aquatic and terrestrial elements that contribute distinctively to the natural capital of arid landscapes. Riparian vegetation is a major component of riparian systems, providing the ecosystem services required to support watershed health. The spatial and temporal distributions of riparian vegetation are influenced by hydrologic and disturbance processes operating at scales from local to regional. I believe both these processes are well suited to monitoring using synoptic and multitemporal approaches. The research in this dissertation is presented as 3 related studies. The first study focused on historical riparian dynamics related to natural disturbance and land use. Using current and historical riparian vegetation maps, we examined vegetation change within catchments of varying land use intensity. Results suggest that land use activities and wastewater subsidy affect the rate of development and diversity of riparian community types. The second study used moderate resolution satellite imagery to monitor changes in riparian structure and pattern within a land cover change framework. We classified Landsat Thematic Mapper satellite imagery of the Upper Santa Cruz River watershed using Classification and Regression Tree (CART) models. We tested the ability of our models to capture change at landscape, floodplain, and catchment scales, centering our change detection efforts on a riparian tree die-off episode and found they can be used to describe both general landscape dynamics and disturbance-related riparian change. The third study examined historical and environmental factors contributing to spatial patterns of vegetation following two riparian tree die-offs. We used high resolution aerial imagery to map locations of individual live and dead trees and collected a suite of environmental variables and historical variables related directly and indirectly to land use and disturbance history. We tested for differences between
Lyon, Aaron R.; Maras, Melissa A.; Pate, Christina M.; Igusa, Takeru; Stoep, Ann Vander
2016-01-01
Although it is widely known that the occurrence of depression increases over the course of adolescence, symptoms of mood disorders frequently go undetected. While schools are viable settings for conducting universal screening to systematically identify students in need of services for common health conditions, particularly those that adversely affect school performance, few school districts routinely screen their students for depression. Among the most commonly referenced barriers are concerns that the number of students identified may exceed schools’ service delivery capacities, but few studies have evaluated this concern systematically. System dynamics (SD) modeling may prove a useful approach for answering questions of this sort. The goal of the current paper is therefore to demonstrate how SD modeling can be applied to inform implementation decisions in communities. In our demonstration, we used SD modeling to estimate the additional service demand generated by universal depression screening in a typical high school. We then simulated the effects of implementing “compensatory approaches” designed to address anticipated increases in service need through (1) the allocation of additional staff time and (2) improvements in the effectiveness of mental health interventions. Results support the ability of screening to facilitate more rapid entry into services and suggest that improving the effectiveness of mental health services for students with depression via the implementation of an evidence-based treatment protocol may have a limited impact on overall recovery rates and service availability. In our example, the SD approach proved useful in informing systems’ decision-making about the adoption of a new school mental health service. PMID:25601192
Kishi, Ryohei; Fujii, Hiroaki; Minami, Takuya; Shigeta, Yasuteru; Nakano, Masayoshi
2015-01-22
In this study, we apply the ab initio molecular orbital - configuration interaction based quantum master equation (MOQME) approach to the calculation and analysis of the dynamic first hyperpolarizabilities (β) of asymmetric π-conjugated molecules. In this approach, we construct the excited state models by the ab initio configuration interaction singles method. Then, time evolutions of system reduced density matrix ρ(t) and system polarization p(t) are calculated by the QME approach. Dynamic β in the second harmonic generation is calculated based on the nonperturbative definition of nonlinear optical susceptibility, using the frequency domain system polarization p(ω). Spatial contributions of electrons to β are analyzed based on the dynamic hyperpolarizability density map, which visualizes the second-order response of charge density oscillating with a frequency of 2ω. We apply the present method to the calculation of the dynamic β of a series of donor/acceptor substituted polyene oligomers, and then discuss the applicability of the MOQME method to the calculation and analysis of dynamic NLO properties of molecular systems.
Ertaş, Mehmet; Deviren, Bayram; Keskin, Mustafa
2012-11-01
Nonequilibrium magnetic properties in a two-dimensional kinetic mixed spin-2 and spin-5/2 Ising system in the presence of a time-varying (sinusoidal) magnetic field are studied within the effective-field theory (EFT) with correlations. The time evolution of the system is described by using Glauber-type stochastic dynamics. The dynamic EFT equations are derived by employing the Glauber transition rates for two interpenetrating square lattices. We investigate the time dependence of the magnetizations for different interaction parameter values in order to find the phases in the system. We also study the thermal behavior of the dynamic magnetizations, the hysteresis loop area, and dynamic correlation. The dynamic phase diagrams are presented in the reduced magnetic field amplitude and reduced temperature plane and we observe that the system exhibits dynamic tricritical and reentrant behaviors. Moreover, the system also displays a double critical end point (B), a zero-temperature critical point (Z), a critical end point (E), and a triple point (TP). We also performed a comparison with the mean-field prediction in order to point out the effects of correlations and found that some of the dynamic first-order phase lines, which are artifacts of the mean-field approach, disappeared.
2016-08-01
Multi-scale Physics -Based Approach Towards Developing a Greater Understanding of Dynamically Loaded Heterogeneous Systems Distribution Statement A...MATERIALS (TOPIC H): HDTRA 1-09-1-0045 A MULTI-SCALE PHYSICS -BASED APPROACH TOWARDS DEVELOPING A GREATER UNDERSTANDING OF DYNAMICALLY Sb. GRANT NUMBER...4.535 924 × 10 –1 kilogram (kg) unified atomic mass unit (amu) 1.660 539 × 10 –27 kilogram (kg) pound-mass per cubic foot (lb ft –3 ) 1.601 846
NASA Astrophysics Data System (ADS)
Emmi, P. C.; Forster, C. B.; Mills, J. I.; Call, B. D.; Sabula, J.; Klewicki, J. C.; Pataki, D. E.; Peterson, T. R.
2004-12-01
risks associated with declining air quality. The dynamic simulation of urban systems demonstrates that a suite of policies can be found to diminish sprawl and defeat traffic congestion thereby safeguarding the vitality a city. A systems thinking approach, facilitated by a community engagement process, has further enabled community opinion leaders and policy makers to map the key features, linkages and feedbacks of a complex, CO2-emitting urban ecosystem. A corresponding lumped-parameter, simulation model provides a framework for decision makers and stakeholders to explore the consequences of alternative options for managing urban growth, sprawl and congestion while also reducing CO2 emissions.
Omer, Ankur; Singh, Poonam
2017-05-01
A serious challenge in cancer treatment is to reposition the activity of various already known drug candidates against cancer. There is a need to rewrite and systematically analyze the detailed mechanistic aspect of cellular networks to gain insight into the novel role played by various molecules. Most Human Immunodeficiency Virus infection-associated cancers are caused by oncogenic viruses like Human Papilloma Viruses and Epstein-Bar Virus. As the onset of AIDS-associated cancers marks the severity of AIDS, there might be possible interconnections between the targets and mechanism of both the diseases. We have explored the possibility of certain antiviral compounds to act against major AIDS-associated cancers: Kaposi's Sarcoma, Non-Hodgkin Lymphoma, and Cervical Cancer with the help of systems pharmacology approach that includes screening for targets and molecules through the construction of a series of drug-target and drug-target-diseases network. Two molecules (Calanolide A and Chaetochromin B) and the target "HRAS" were finally screened with the help of molecular docking and molecular dynamics simulation. The results provide novel antiviral molecules against HRAS target to treat AIDS defining cancers and an insight for understanding the pharmacological, therapeutic aspects of similar unexplored molecules against various cancers.
Coupled nonlinear dynamical systems
NASA Astrophysics Data System (ADS)
Sun, Hongyan
In this dissertation, we study coupled nonlinear dynamical systems that exhibit new types of complex behavior. We numerically and analytically examine a variety of dynamical models, ranging from systems of ordinary differential equations (ODE) with novel elements of feedback to systems of partial differential equations (PDE) that model chemical pattern formation. Chaos, dynamical uncertainty, synchronization, and spatiotemporal pattern formation constitute the primary topics of the dissertation. Following the introduction in Chapter 1, we study chaos and dynamical uncertainty in Chapter 2 with coupled Lorenz systems and demonstrate the existence of extreme complexity in high-dimensional ODE systems. In Chapter 3, we demonstrate that chaos synchronization can be achieved by mutual and multiplicative coupling of dynamical systems. Chapter 4 and 5 focus on pattern formation in reaction-diffusion systems, and we investigate segregation and integration behavior of populations in competitive and cooperative environments, respectively.
Systems With Emergent Dynamics
NASA Astrophysics Data System (ADS)
Stewart, Ian
2002-09-01
Evolutionary biologists often reject deterministic models of evolutionary processes because they equate `deterministic' with `goal-seeking', and have learned the hard way not to trust goal-seeking explanations of evolutionary adaptations. On the other hand, the general theory of dynamical systems potentially has much to offer for evolutionary biology— for example, as a resolution of the conflict between gradualism and punctuated equilibrium. The concept of a system with emergent dynamics retains the deterministic nature of dynamical systems, while eliminating any goal-seeking interpretation. Define an emergent property of a complex system to be a property whose computation from the entity-level rules of the system is intractable (in some reasonable sense). Say that a dynamical system has emergent dynamics if the computation of trajectories is intractable. Then systems with emergent dynamics are deterministic but not goal-seeking. As such, they offer a sensible way to use dynamical systems as models for evolutionary processes in biology, and in other areas. We discuss these issues and examine a few simple aspects of emergence in dynamical systems.
Sheeley, Douglas M; Breen, Joseph J; Old, Susan E
2005-01-01
Proteomics technology and methods remain inadequate. Technological constraints contribute to an artificially static view of complex biological systems and a barrier between quantitative and interaction studies. Several NIH programs combine proteomics technology development with research on challenging biological problems to drive progress. A new initiative of the NIH Roadmap focuses on characterization of dynamic systems. The success of these programs will be judged by their impact on relevant biological problems.
Extensible Systems Dynamics Framework
2008-04-01
pedigree information across communities-of-interest and across network boundaries. 15. SUBJECT TERMS Ptolemy II, Systems Dynamics, PMESII, National...3 4.2 ADAPT THE PTOLEMY II FRAMEWORK TO ENSURE A WELL-SUITED MODELING...report of activities in the Extensible Systems Dynamics Framework project performed by the Ptolemy Project, University of California, Berkeley for
Physical science: A dynamic approach
Dixon, R.T.
1986-01-01
A partial table of contents is: Early concepts of nature. The rebirth of science. Energy, work, and power. Relativity. The atom. The periodic nature of elements. Chemical energy. The dynamic Earth. The solar system. Stars and nebulae. Extraterrestrial life. The author presents an introduction to physical science and the spirit of scientific inquiry through a historical survey of scientific thought. Specific forces, processes, energies and phenomena are outlined. Various tables, illustrations and questions accompany the text.
NASA Astrophysics Data System (ADS)
Zakhari, Monica E. A.; Anderson, Patrick D.; Hütter, Markus
2017-07-01
Open-porous deformable particles, often envisaged as sponges, are ubiquitous in biological and industrial systems (e.g., casein micelles in dairy products and microgels in cosmetics). The rich behavior of these suspensions is owing to the elasticity of the supporting network of the particle, and the viscosity of permeating solvent. Therefore, the rate-dependent size change of these particles depends on their structure, i.e., the permeability. This work aims at investigating the effect of the particle-size dynamics and the underlying particle structure, i.e., the particle permeability, on the transient and long-time behavior of suspensions of spongy particles in the absence of applied deformation, using the dynamic two-scale model developed by Hütter et al. [Farad. Discuss. 158, 407 (2012), 10.1039/c2fd20025b]. In the high-density limit, the transient behavior is found to be accelerated by the particle-size dynamics, even at average size changes as small as 1 % . The accelerated dynamics is evidenced by (i) the higher short-time diffusion coefficient as compared to elastic-particle systems and (ii) the accelerated formation of the stable fcc crystal structure. Furthermore, after long times, the particle-size dynamics of spongy particles is shown to result in lower stationary values of the energy and normal stresses as compared to elastic-particle systems. This dependence of the long-time behavior of these systems on the permeability, that essentially is a transport coefficient and hence must not affect the equilibrium properties, confirms that full equilibration has not been reached.
Dynamical maximum entropy approach to flocking
NASA Astrophysics Data System (ADS)
Cavagna, Andrea; Giardina, Irene; Ginelli, Francesco; Mora, Thierry; Piovani, Duccio; Tavarone, Raffaele; Walczak, Aleksandra M.
2014-04-01
We derive a new method to infer from data the out-of-equilibrium alignment dynamics of collectively moving animal groups, by considering the maximum entropy model distribution consistent with temporal and spatial correlations of flight direction. When bird neighborhoods evolve rapidly, this dynamical inference correctly learns the parameters of the model, while a static one relying only on the spatial correlations fails. When neighbors change slowly and the detailed balance is satisfied, we recover the static procedure. We demonstrate the validity of the method on simulated data. The approach is applicable to other systems of active matter.
NASA Astrophysics Data System (ADS)
Roberson, Robert E.; Schwertassek, Richard
The fundamental mathematical principles of multibody-system dynamics and their implementation in numerical simulations are examined in a rigorous introduction for design engineers. Chapters are devoted to the history of rotational dynamics; typical spacecraft, vehicle, and robotics applications; terminology and notation; the kinematics of a rigid body (location and orientation, velocity, and the kinematical equations of motion); the dynamics of a rigid body; multibody formalisms, kinematics, and dynamics; the linearized equations for multibody systems; and computer simulation techniques. Diagrams, drawings, and a glossary of symbols are provided.
The Modern Temperature-Accelerated Dynamics Approach.
Zamora, Richard J; Uberuaga, Blas P; Perez, Danny; Voter, Arthur F
2016-06-07
Accelerated molecular dynamics (AMD) is a class of MD-based methods used to simulate atomistic systems in which the metastable state-to-state evolution is slow compared with thermal vibrations. Temperature-accelerated dynamics (TAD) is a particularly efficient AMD procedure in which the predicted evolution is hastened by elevating the temperature of the system and then recovering the correct state-to-state dynamics at the temperature of interest. TAD has been used to study various materials applications, often revealing surprising behavior beyond the reach of direct MD. This success has inspired several algorithmic performance enhancements, as well as the analysis of its mathematical framework. Recently, these enhancements have leveraged parallel programming techniques to enhance both the spatial and temporal scaling of the traditional approach. We review the ongoing evolution of the modern TAD method and introduce the latest development: speculatively parallel TAD.
The modern temperature-accelerated dynamics approach
Zamora, Richard J.; Uberuaga, Blas P.; Perez, Danny; ...
2016-06-01
Accelerated molecular dynamics (AMD) is a class of MD-based methods used to simulate atomistic systems in which the metastable state-to-state evolution is slow compared with thermal vibrations. Temperature-accelerated dynamics (TAD) is a particularly efficient AMD procedure in which the predicted evolution is hastened by elevating the temperature of the system and then recovering the correct state-to-state dynamics at the temperature of interest. TAD has been used to study various materials applications, often revealing surprising behavior beyond the reach of direct MD. This success has inspired several algorithmic performance enhancements, as well as the analysis of its mathematical framework. Recently, thesemore » enhancements have leveraged parallel programming techniques to enhance both the spatial and temporal scaling of the traditional approach. Here, we review the ongoing evolution of the modern TAD method and introduce the latest development: speculatively parallel TAD.« less
The modern temperature-accelerated dynamics approach
Zamora, Richard J.; Uberuaga, Blas P.; Perez, Danny; Voter, Arthur F.
2016-06-01
Accelerated molecular dynamics (AMD) is a class of MD-based methods used to simulate atomistic systems in which the metastable state-to-state evolution is slow compared with thermal vibrations. Temperature-accelerated dynamics (TAD) is a particularly efficient AMD procedure in which the predicted evolution is hastened by elevating the temperature of the system and then recovering the correct state-to-state dynamics at the temperature of interest. TAD has been used to study various materials applications, often revealing surprising behavior beyond the reach of direct MD. This success has inspired several algorithmic performance enhancements, as well as the analysis of its mathematical framework. Recently, these enhancements have leveraged parallel programming techniques to enhance both the spatial and temporal scaling of the traditional approach. Here, we review the ongoing evolution of the modern TAD method and introduce the latest development: speculatively parallel TAD.
The modern temperature-accelerated dynamics approach
Zamora, Richard J.; Uberuaga, Blas P.; Perez, Danny; Voter, Arthur F.
2016-06-01
Accelerated molecular dynamics (AMD) is a class of MD-based methods used to simulate atomistic systems in which the metastable state-to-state evolution is slow compared with thermal vibrations. Temperature-accelerated dynamics (TAD) is a particularly efficient AMD procedure in which the predicted evolution is hastened by elevating the temperature of the system and then recovering the correct state-to-state dynamics at the temperature of interest. TAD has been used to study various materials applications, often revealing surprising behavior beyond the reach of direct MD. This success has inspired several algorithmic performance enhancements, as well as the analysis of its mathematical framework. Recently, these enhancements have leveraged parallel programming techniques to enhance both the spatial and temporal scaling of the traditional approach. Here, we review the ongoing evolution of the modern TAD method and introduce the latest development: speculatively parallel TAD.
Systems Science Approach to Data
NASA Astrophysics Data System (ADS)
Kadirkamanathan, Visakan
Behaviours of many complex systems of interest cannot be adequately described since the underlying science has not advanced enough to be able to tease out the mathematical relationships. There is a need therefore to use methods and tools that capture the structure in the data that is representative of the systems behaviour. The subject of system identification allows us to deduce mathematical relations that govern the dynamics of systems based on the observed data. In addition, it can also be used to understand the system from basic principles. In this brief talk, the main approaches of systems science to data are reviewed identifying their strengths and limitations. The approaches include computational intelligence methods such as neural networks, genetic algorithms and fuzzy logic, as well as system identification methods in both time and frequency domains. Examples from physical science, neuroscience and social science serve to highlight achievements of the systems science approach to data.
Mass properties measurement system dynamics
NASA Technical Reports Server (NTRS)
Doty, Keith L.
1993-01-01
The MPMS mechanism possess two revolute degrees-of-freedom and allows the user to measure the mass, center of gravity, and the inertia tensor of an unknown mass. The dynamics of the Mass Properties Measurement System (MPMS) from the Lagrangian approach to illustrate the dependency of the motion on the unknown parameters.
Markutsya, Sergiy; Lamm, Monica H.
2014-11-07
We report on a new approach for deriving coarse-grained intermolecular forces that retains the frictional contribution that is often discarded by conventional coarse-graining methods. The approach is tested for water and an aqueous glucose solution, and the results from the new implementation for coarse-grained molecular dynamics simulation show remarkable agreement with the dynamics obtained from reference all-atom simulations. The agreement between the structural properties observed in the coarse-grained and all-atom simulations is also preserved. We discuss how this approach may be applied broadly to any existing coarse-graining method where the coarse-grained models are rigorously derived from all-atom reference systems.
NASA Astrophysics Data System (ADS)
Markutsya, Sergiy; Lamm, Monica H.
2014-11-01
We report on a new approach for deriving coarse-grained intermolecular forces that retains the frictional contribution that is often discarded by conventional coarse-graining methods. The approach is tested for water and an aqueous glucose solution, and the results from the new implementation for coarse-grained molecular dynamics simulation show remarkable agreement with the dynamics obtained from reference all-atom simulations. The agreement between the structural properties observed in the coarse-grained and all-atom simulations is also preserved. We discuss how this approach may be applied broadly to any existing coarse-graining method where the coarse-grained models are rigorously derived from all-atom reference systems.
Dynamical Systems++ for a Theory of Biological System
NASA Astrophysics Data System (ADS)
Kaneko, Kunihiko
2014-12-01
Biological dynamical systems can autonomously change their rule governing the dynamics. To deal with the change in their rule, possible approaches to extend dynamical-systems theory are discussed: They include chaotic itinerancy in high-dimensional dynamical systems, discreteness-induced switches of states, and interference between slow and fast modes. Applications of these concepts to cell differentiation, adaptation, and memory are briefly reviewed, while biological evolution is discussed as selection of dynamical systems by dynamical systems. Finally, necessity of mathematical framework to deal with self-referential dynamics for the rule formation is stressed.
Time-resolved spectroscopy at surfaces and adsorbate dynamics:insights from a model-system approach
NASA Astrophysics Data System (ADS)
Boström, Emil; Mikkelsen, Anders; Verdozzi, Claudio
We introduce a finite-system, model description of the initial stages of femtosecond laser induced desorption at surfaces. Using the exact many-body time evolution and also results from a novel time-dependent DFT description for electron-nuclear systems, we analyse the competition between several surface-response mechanisms and electronic correlations in the transient and longer time dynamics under the influence of dipole-coupled fields. Our model allows us to explore how coherent multiple-pulse protocols impact desorption in a variety of prototypical experiments.
Shafaghati, Leila; Razaghi-Moghadam, Zahra; Mohammadnejad, Javad
2017-08-28
Alcoholic liver disease (ALD) is a complex disease characterized by damages to the liver and is the consequence of excessive alcohol consumption over years. Since this disease is associated with several pathway failures, pathway reconstruction and network analysis are likely to explicit the molecular basis of the disease. To this aim, in this paper, a network medicine approach was employed to integrate interactome (protein-protein interaction and signaling pathways) and transcriptome data to reconstruct both a static network of ALD and a dynamic model for it. Several data sources were exploited to assemble a set of ALD-associated genes which further was used for network reconstruction. Moreover, a comprehensive literature mining reveals that there are four signaling pathways with crosstalk (TLR4, NF- [Formula: see text]B, MAPK and Apoptosis) which play a major role in ALD. These four pathways were exploited to reconstruct a dynamic model of ALD. The results assure that these two models are consistent with a number of experimental observations. The static network of ALD and its dynamic model are the first models provided for ALD which offer potentially valuable information for researchers in this field.
Vulnerability of dynamic systems
NASA Technical Reports Server (NTRS)
Siljak, D. D.
1976-01-01
Directed graphs are associated with dynamic systems in order to determine in any given system if each state can be reached by at least one input (input reachability), or can each state reach at least one output (output reachability). Then, the structural perturbations of a dynamic system are identified as lines or points removals from the corresponding digraph, and a system is considered vulnerable at those lines or points of the digraph whose removal destroys its input or output reachability. A suitable framework is formulated for resolving the problems of reachability and vulnerability which applies to both linear and nonlinear systems alike.
NASA Technical Reports Server (NTRS)
Griffin, Brian Joseph; Burken, John J.; Xargay, Enric
2010-01-01
This paper presents an L(sub 1) adaptive control augmentation system design for multi-input multi-output nonlinear systems in the presence of unmatched uncertainties which may exhibit significant cross-coupling effects. A piecewise continuous adaptive law is adopted and extended for applicability to multi-input multi-output systems that explicitly compensates for dynamic cross-coupling. In addition, explicit use of high-fidelity actuator models are added to the L1 architecture to reduce uncertainties in the system. The L(sub 1) multi-input multi-output adaptive control architecture is applied to the X-29 lateral/directional dynamics and results are evaluated against a similar single-input single-output design approach.
NASA Technical Reports Server (NTRS)
Doolin, B. F.
1975-01-01
Classes of large scale dynamic systems were discussed in the context of modern control theory. Specific examples discussed were in the technical fields of aeronautics, water resources and electric power.
Dynamics of collisionless systems
NASA Technical Reports Server (NTRS)
Zang, T. A.
1980-01-01
The three dimensional dynamics of rotating stellar systems were studied. A comparison of various mathematical models of flat galaxies is presented. The effects of self-gravity upon a flat galaxy undergoing a tidal encounter with another galaxy were investigated.
NASA Astrophysics Data System (ADS)
Sutrisno; Widowati; Heru Tjahjana, R.
2017-01-01
In this paper, we propose a mathematical model in the form of dynamic/multi-stage optimization to solve an integrated supplier selection problem and tracking control problem of single product inventory system with product discount. The product discount will be stated as a piece-wise linear function. We use dynamic programming to solve this proposed optimization to determine the optimal supplier and the optimal product volume that will be purchased from the optimal supplier for each time period so that the inventory level tracks a reference trajectory given by decision maker with minimal total cost. We give a numerical experiment to evaluate the proposed model. From the result, the optimal supplier was determined for each time period and the inventory level follows the given reference well.
Epilogue: Systems Approaches and Systems Practice
NASA Astrophysics Data System (ADS)
Reynolds, Martin; Holwell, Sue
Each of the five systems approaches discussed in this volume: system dynamics (SD), the viable systems model (VSM), strategic options development and analysis (SODA), soft systems methodology (SSM) and critical systems heuristics (CSH) has a pedigree. Not in the sense of the sometimes absurd spectacle of animals paraded at dog shows. Rather, their pedigree derives from their systems foundations, their capacity to evolve and their flexibility in use. None of the five approaches has developed out of use in restricted and controlled contexts of either low or high levels of complicatedness. Neither has any one of them evolved as a consequence of being applied only to situations with either presumed stakeholder agreement on purpose, or courteous disagreement amongst stakeholders, or stakeholder coercion. The compilation is not a celebration of abstract ‘methodologies', but of theoretically robust approaches that have a genuine pedigree in practice.
NASA Technical Reports Server (NTRS)
Ghosh, Bijoy K.
1988-01-01
This paper studies structured uncertainty problems in feedback system design, considers a compact parameterization of the space of linear dynamical systems and introduces 'base points' and 'critical points' as two algebraic-geometric objects that have significance in sensitivity and robustness studies, respectively. Using the Nevanlinna-Pick interpolation theory, the author obtains a necessary and sufficient condition for simultaneous stabilization of a structured one-parameter family of plants. A recent result due to Kharitonov, on the simultaneous stability of a parameterized family of polynomials, leads to a sufficiency condition for simultaneous stabilization of a structured multiparameter family of plants. Furthermore, the author considers 'simultaneous pole placement' of an r-tuple of plants as a means to arbitrarily tune the natural frequencies of a multimode linear dynamical system. The concept of 'nondegenerate' and 'twisted' r-tuples of plants is introduced as the pole placement problem is studied via Schubert enumerative geometry as an intersection problem on the associated Grassmannian. Various other design problems, viz., the strong stabilization problem and the dead beat control problem, are also considered.
Al-Khatib, Issam A; Eleyan, Derar; Garfield, Joy
2016-09-01
Hospitals and health centers provide a variety of healthcare services and normally generate hazardous waste as well as general waste. General waste has a similar nature to that of municipal solid waste and therefore could be disposed of in municipal landfills. However, hazardous waste poses risks to public health, unless it is properly managed. The hospital waste management system encompasses many factors, i.e., number of beds, number of employees, level of service, population, birth rate, fertility rate, and not in my back yard (NIMBY) syndrome. Therefore, this management system requires a comprehensive analysis to determine the role of each factor and its influence on the whole system. In this research, a hospital waste management simulation model is presented based on the system dynamics technique to determine the interaction among these factors in the system using a software package, ithink. This model is used to estimate waste segregation as this is important in the hospital waste management system to minimize risk to public health. Real data has been obtained from a case study of the city of Nablus, Palestine to validate the model. The model exhibits wastes generated from three types of hospitals (private, charitable, and government) by considering the number of both inpatients and outpatients depending on the population of the city under study. The model also offers the facility to compare the total waste generated among these different types of hospitals and anticipate and predict the future generated waste both infectious and non-infectious and the treatment cost incurred.
Lagny, Thibaut J.; Bassereau, Patricia
2015-01-01
Being at the periphery of each cell compartment and enclosing the entire cell while interacting with a large part of cell components, cell membranes participate in most of the cell's vital functions. Biologists have worked for a long time on deciphering how membranes are organized, how they contribute to trafficking, motility, cytokinesis, cell–cell communication, information transport, etc., using top-down approaches and always more advanced techniques. In contrast, physicists have developed bottom-up approaches and minimal model membrane systems of growing complexity in order to build up general models that explain how cell membranes work and how they interact with proteins, e.g. the cytoskeleton. We review the different model membrane systems that are currently available, and how they can help deciphering cell functioning, but also list their limitations. Model membrane systems are also used in synthetic biology and can have potential applications beyond basic research. We discuss the possible synergy between the development of complex in vitro membrane systems in a biological context and for technological applications. Questions that could also be discussed are: what can we still do with synthetic systems, where do we stop building up and which are the alternative solutions? PMID:26464792
Biologically inspired dynamic material systems.
Studart, André R
2015-03-09
Numerous examples of material systems that dynamically interact with and adapt to the surrounding environment are found in nature, from hair-based mechanoreceptors in animals to self-shaping seed dispersal units in plants to remodeling bone in vertebrates. Inspired by such fascinating biological structures, a wide range of synthetic material systems have been created to replicate the design concepts of dynamic natural architectures. Examples of biological structures and their man-made counterparts are herein revisited to illustrate how dynamic and adaptive responses emerge from the intimate microscale combination of building blocks with intrinsic nanoscale properties. By using top-down photolithographic methods and bottom-up assembly approaches, biologically inspired dynamic material systems have been created 1) to sense liquid flow with hair-inspired microelectromechanical systems, 2) to autonomously change shape by utilizing plantlike heterogeneous architectures, 3) to homeostatically influence the surrounding environment through self-regulating adaptive surfaces, and 4) to spatially concentrate chemical species by using synthetic microcompartments. The ever-increasing complexity and remarkable functionalities of such synthetic systems offer an encouraging perspective to the rich set of dynamic and adaptive properties that can potentially be implemented in future man-made material systems. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
NASA Astrophysics Data System (ADS)
Nourmandipour, A.; Tavassoly, M. K.
2015-08-01
In this paper, we study the exact entanglement dynamics of two two-level atoms in a dissipative cavity. We use the Gardiner-Collett Hamiltonian to model the dissipative cavity, in which we assume that the two atoms resonantly interact with the cavity field and the cavity field itself interacts with the surrounding medium. Then, with the help of the Fano’s technique we show that this system can be regarded as two atoms interacting with a heat bath. In such a case, we find that there exists a decoherence-free state that does not evolve in time. At this time there exists a so-called super-radiant state which decays in time due to dissipation. At last, we use the quantum Zeno effect to preserve the entanglement which already has been stored in the system.
Long timestep dynamics of peptides by the dynamics driver approach.
Derreumaux, P; Schlick, T
1995-04-01
Previous experience with the Langevin/implicit-Euler scheme for dynamics ("LI") on model systems (butane, water) has shown that LI is numerically stable for timesteps in the 5-20 fs range but quenches high-frequency modes. To explore applications to polypeptides, we apply LI to model systems (several dipeptides, a tetrapeptide, and a 13-residue oligoalanine) and also develop a new dynamics driver approach ("DA"). The DA scheme, based on LI, addresses the important issue of proper sampling, which is unlikely to be solved by small-timestep integration methods or implicit methods with intrinsic damping at room temperature, such as LI. Equilibrium averages, time-dependent molecular properties, and sampling trends at room temperature are reported for both LI and DA dynamics simulations, which are then compared to those generated by a standard explicit discretization of the Langevin equation with a 1 fs timestep. We find that LI's quenching effects are severe on both the fast and slow (due to vibrational coupling) frequency modes of all-atom polypeptides and lead to more restricted dynamics at moderate timesteps (40 fs). The DA approach empirically counteracts these damping effects by adding random atomic perturbations to the coordinates at each step (before the minimization of a dynamics function). By restricting the energetic fluctuations and controlling the kinetic energy, we are able with a 60 fs timestep to generate continuous trajectories that sample more of the relevant conformational space and also reproduce reasonably Boltzmann statistics. Although the timescale for transition may be accelerated by the DA approach, the transitional information obtained for the alanine dipeptide and the tetrapeptide is consistent with that obtained by several other theoretical approaches that focus specifically on the determination of pathways. While the trajectory for oligoalanine by the explicit scheme over the nanosecond timeframe remains in the vicinity of the full alpha R
Quantum electron-vibrational dynamics at finite temperature: Thermo field dynamics approach.
Borrelli, Raffaele; Gelin, Maxim F
2016-12-14
Quantum electron-vibrational dynamics in molecular systems at finite temperature is described using an approach based on the thermo field dynamics theory. This formulation treats temperature effects in the Hilbert space without introducing the Liouville space. A comparison with the theoretically equivalent density matrix formulation shows the key numerical advantages of the present approach. The solution of thermo field dynamics equations with a novel technique for the propagation of tensor trains (matrix product states) is discussed. Numerical applications to model spin-boson systems show that the present approach is a promising tool for the description of quantum dynamics of complex molecular systems at finite temperature.
Semipredictable dynamical systems
NASA Astrophysics Data System (ADS)
García-Morales, Vladimir
2016-10-01
A new class of deterministic dynamical systems, termed semipredictable dynamical systems, is presented. The spatiotemporal evolution of these systems have both predictable and unpredictable traits, as found in natural complex systems. We prove a general result: The dynamics of any deterministic nonlinear cellular automaton (CA) with p possible dynamical states can be decomposed at each instant of time in a superposition of N layers involving p0, p1, …, pN - 1 dynamical states each, where the pk ∈ N , k ∈ [ 0 , N - 1 ] are divisors of p. If the divisors coincide with the prime factors of p this decomposition is unique. Conversely, we also prove that N CA working on symbols p0, p1, …, pN - 1 can be composed to create a graded CA rule with N different layers. We then show that, even when the full spatiotemporal evolution can be unpredictable, certain traits (layers) can exactly be predicted. We present explicit examples of such systems involving compositions of Wolfram's 256 elementary CA and a more complex CA rule acting on a neighborhood of two sites and 12 symbols and whose rule table corresponds to the smallest Moufang loop M12(S3, 2).
Semiclassical approaches to nuclear dynamics
NASA Astrophysics Data System (ADS)
Magner, A. G.; Gorpinchenko, D. V.; Bartel, J.
2017-01-01
The extended Gutzwiller trajectory approach is presented for the semiclassical description of nuclear collective dynamics, in line with the main topics of the fruitful activity of V.G. Solovjov. Within the Fermi-liquid droplet model, the leptodermous effective surface approximation was applied to calculations of energies, sum rules, and transition densities for the neutron-proton asymmetry of the isovector giant-dipole resonance and found to be in good agreement with the experimental data. By using the Strutinsky shell correctionmethod, the semiclassical collective transport coefficients, such as nuclear inertia, friction, stiffness, and moments of inertia, can be derived beyond the quantum perturbation approximation of the response function theory and the cranking model. The averaged particle-number dependences of the low-lying collective vibrational states are described in good agreement with the basic experimental data, mainly due to the enhancement of the collective inertia as compared to its irrotational flow value. Shell components of the moment of inertia are derived in terms of the periodic-orbit free-energy shell corrections. A good agreement between the semiclassical extended Thomas-Fermi moments of inertia with shell corrections and the quantum results is obtained for different nuclear deformations and particle numbers. Shell effects are shown to be exponentially dampted out with increasing temperature in all the transport coefficients.
Systems biology approach to bioremediation
Chakraborty, Romy; Wu, Cindy H.; Hazen, Terry C.
2012-06-01
Bioremediation has historically been approached as a ‘black box’ in terms of our fundamental understanding. Thus it succeeds and fails, seldom without a complete understanding of why. Systems biology is an integrated research approach to study complex biological systems, by investigating interactions and networks at the molecular, cellular, community, and ecosystem level. The knowledge of these interactions within individual components is fundamental to understanding the dynamics of the ecosystem under investigation. Finally, understanding and modeling functional microbial community structure and stress responses in environments at all levels have tremendous implications for our fundamental understanding of hydrobiogeochemical processes and the potential for making bioremediation breakthroughs and illuminating the ‘black box’.
Schwartz, Brian; Palma, Anton
2015-01-01
Abstract System dynamics (SD) modeling belongs to the rapidly evolving, interdisciplinary field of system science research. This field adds value to more traditional health research by contributing to the design and testing of complex integrated models of change, to examine health system performance and patient outcomes. Using selected milestones in HIV care management to frame our simulation research, we created a SD model to examine three patient subgroups of women of color (WOC) represented in our multi-site cohort, classified by their health care seeking status at baseline. Asked to reflect on their circumstance 6 months prior to enrollment in the MSE cohort, 53% noted they were receiving some care (In Care, n=341), 31% that they had been seeking care (Seeking Care, n=201), and 16% that they were undecided about seeking care (i.e., answered that they may or may not look for care) for treatment of their HIV (May or May Not Seek Care, n=103). Our SD model compared simulated patterns of patient retention over 24 months in relation to: (1) access to antiretroviral therapy (ART), (2) adherence to ART, and (3) viral suppression. Assessed patterns yielded insights about system capacities and constraints in the context of the SPNS initiative under evaluation. PMID:25561309
NASA Astrophysics Data System (ADS)
Syahdan, A. D.; Arkeman, Y.; Wijaya, H.
2017-05-01
Biodiesel is one of the alternative fuels that are environmentally friendly. Besides palm oil, biodiesel can also be produced from waste cooking oil. Since 2007, the government of Bogor has been utilizing waste cooking oil into biodiesel for use as Transpakuan bus’ fuel. However, in practice, the amount of waste cooking oil supplied is never sufficient the needs of fuel of 30 units Transpakuan bus. The main objective of this research is to analyze the availability of waste cooking oil that will be converted into biodiesel within the next ten years as well as providing policy advice to support the program. The method used is a dynamic system that is followed by simulation of multiple scenarios that have been defined. The system is divided into three subsystems, namely supply subsystem, demand subsystem, and production subsystem. The results showed that the current system is not able to guarantee the sustainability of the supply chain of waste cooking oil as a raw material of biodiesel. From some of the scenarios tested can be concluded that biodiesel needs would increase in line with the trend of the use of environmentally friendly fuels. It takes a new system and a new policy relating to the biodiesel supply chain. Policy suggestions that can be proposed from this research is to increase supplier participation, objectify the program of converting angkot into Transpakuan bus, and support the development of biodiesel industry.
NASA Astrophysics Data System (ADS)
Pumpe, Daniel; Greiner, Maksim; Müller, Ewald; Enßlin, Torsten A.
2016-07-01
Stochastic differential equations describe well many physical, biological, and sociological systems, despite the simplification often made in their derivation. Here the usage of simple stochastic differential equations to characterize and classify complex dynamical systems is proposed within a Bayesian framework. To this end, we develop a dynamic system classifier (DSC). The DSC first abstracts training data of a system in terms of time-dependent coefficients of the descriptive stochastic differential equation. Thereby the DSC identifies unique correlation structures within the training data. For definiteness we restrict the presentation of the DSC to oscillation processes with a time-dependent frequency ω (t ) and damping factor γ (t ) . Although real systems might be more complex, this simple oscillator captures many characteristic features. The ω and γ time lines represent the abstract system characterization and permit the construction of efficient signal classifiers. Numerical experiments show that such classifiers perform well even in the low signal-to-noise regime.
Pumpe, Daniel; Greiner, Maksim; Müller, Ewald; Enßlin, Torsten A
2016-07-01
Stochastic differential equations describe well many physical, biological, and sociological systems, despite the simplification often made in their derivation. Here the usage of simple stochastic differential equations to characterize and classify complex dynamical systems is proposed within a Bayesian framework. To this end, we develop a dynamic system classifier (DSC). The DSC first abstracts training data of a system in terms of time-dependent coefficients of the descriptive stochastic differential equation. Thereby the DSC identifies unique correlation structures within the training data. For definiteness we restrict the presentation of the DSC to oscillation processes with a time-dependent frequency ω(t) and damping factor γ(t). Although real systems might be more complex, this simple oscillator captures many characteristic features. The ω and γ time lines represent the abstract system characterization and permit the construction of efficient signal classifiers. Numerical experiments show that such classifiers perform well even in the low signal-to-noise regime.
Complexity in Dynamical Systems
NASA Astrophysics Data System (ADS)
Moore, Cristopher David
The study of chaos has shown us that deterministic systems can have a kind of unpredictability, based on a limited knowledge of their initial conditions; after a finite time, the motion appears essentially random. This observation has inspired a general interest in the subject of unpredictability, and more generally, complexity; how can we characterize how "complex" a dynamical system is?. In this thesis, we attempt to answer this question with a paradigm of complexity that comes from computer science, we extract sets of symbol sequences, or languages, from a dynamical system using standard methods of symbolic dynamics; we then ask what kinds of grammars or automata are needed a generate these languages. This places them in the Chomsky heirarchy, which in turn tells us something about how subtle and complex the dynamical system's behavior is. This gives us insight into the question of unpredictability, since these automata can also be thought of as computers attempting to predict the system. In the culmination of the thesis, we find a class of smooth, two-dimensional maps which are equivalent to the highest class in the Chomsky heirarchy, the turning machine; they are capable of universal computation. Therefore, these systems possess a kind of unpredictability qualitatively different from the usual "chaos": even if the initial conditions are known exactly, questions about the system's long-term dynamics are undecidable. No algorithm exists to answer them. Although this kind of unpredictability has been discussed in the context of distributed, many-degree-of -freedom systems (for instance, cellular automata) we believe this is the first example of such phenomena in a smooth, finite-degree-of-freedom system.
NASA Astrophysics Data System (ADS)
Armstrong McKay, David I.; Dearing, John A.; Dyke, James G.; Poppy, Guy; Firbank, Les
2016-04-01
The world's population continues to grow rapidly, yet the current demand for food is already resulting in environmental degradation in many regions. As a result, an emerging challenge of the 21st century is how agriculture can simultaneously undergo sustainable intensification and be made more resilient to accelerating climate change. Key to this challenge is: a) finding the "safe and just operating space" for the global agri-environment system that both provides sufficient food for humanity and avoids crossing dangerous planetary boundaries, and b) downscaling this framework from a planetary to a regional scale in order to better inform decision making and incorporate regional dynamics within the planetary boundaries framework. Regional safe operating spaces can be defined and explored using a combination of metrics that indicate the changing status of ecosystem services (both provisioning and regulating), statistical techniques that reveal early warning signals and breakpoints, and dynamical system models of the regional agri-environment system. Initial attempts to apply this methodology have been made in developing countries (e.g. China [Dearing et al., 2012, 2014; Zhang et al., 2015]), but have not yet been attempted in more developed countries, for example the UK. In this study we assess the changes in ecosystem services in two contrasting agricultural regions in the UK, arable-dominated East England and pastoral-dominated South-West England, since the middle of the 20th Century. We identify and establish proxies and indices of various provisioning and regulating services in these two regions and analyse how these have changed over this time. We find that significant degradation of regulating services occurred in Eastern England in the early 1980s, reflecting a period of rapid intensification and escalating fertiliser usage, but that regulating services have begun to recover since 2000 mainly as a result of fertiliser usage decoupling from increasing wheat
Self-Supervised Dynamical Systems
NASA Technical Reports Server (NTRS)
Zak, Michail
2003-01-01
metal aspects of a monad is implemented by feedback from mental to motor dynamics, as represented by the aforementioned fictitious forces. This feedback is what makes the evolution of probability densities nonlinear. The deviation from linear evolution can be characterized, in a sense, as an expression of free will. It has been demonstrated that probability densities can approach prescribed attractors while exhibiting such patterns as shock waves, solitons, and chaos in probability space. The concept of self-supervised dynamical systems has been considered for application to diverse phenomena, including information-based neural networks, cooperation, competition, deception, games, and control of chaos. In addition, a formal similarity between the mathematical structures of self-supervised dynamical systems and of quantum-mechanical systems has been investigated.
Semiclassical approach to dynamics of interacting fermions
NASA Astrophysics Data System (ADS)
Davidson, Shainen M.; Sels, Dries; Polkovnikov, Anatoli
2017-09-01
Understanding the behaviour of interacting fermions is of fundamental interest in many fields ranging from condensed matter to high energy physics. Developing numerically efficient and accurate simulation methods is an indispensable part of this. Already in equilibrium, fermions are notoriously hard to handle due to the sign problem. Out of equilibrium, an important outstanding problem is the efficient numerical simulation of the dynamics of these systems. In this work we develop a new semiclassical phase-space approach (a.k.a. the truncated Wigner approximation) for simulating the dynamics of interacting fermions in arbitrary dimensions. As fermions are essentially non-classical objects, a phase-space is constructed out of all fermionic bilinears. Classical phase-space is thus comprised of highly non-local (hidden) variables representing these bilinears, and the cost of the method is that it scales quadratic rather than linear with system size. We demonstrate the strength of the method by comparing the results to the exact quantum dynamics of fermion expansion in the Hubbard model and quantum thermalization in the Sachdev-Ye-Kitaev (SYK) model for small systems, where the semiclassics nearly perfectly reproduces correct results. We furthermore analyse fermion expansion in a larger, intractable by exact methods, 2D Hubbard model, which is directly relevant to recent cold atom experiments.
Kim, S; Frank, T D
2017-01-01
We report from two variants of a figure-ground experiment that is known in the literature to involve a bistable perceptual domain. The first variant was conducted as a two-alternative forced-choice experiment and in doing so tested participants on a categorical measurement scale. The second variant involved a Likert scale measure that was considered to represent a continuous measurement scale. The two variants were conducted as a single within-subjects experiment. Measures of bistability operationalized in terms of hysteresis size scores showed significant positive correlations across the two response conditions. The experimental findings are consistent with a dualistic interpretation of self-organizing perceptual systems when they are described on a macrolevel by means of so-called amplitude equations. This is explicitly demonstrated for a Lotka-Volterra-Haken amplitude equation model of task-related brain activity. As a by-product, the proposed dynamical systems perspective also sheds new light on the anchoring problem of producing numerical, continuous judgments.
Hamiltonian approach to slip-stacking dynamics
Lee, S. Y.; Ng, K. Y.
2017-06-29
Hamiltonian dynamics has been applied to study the slip-stacking dynamics. The canonical-perturbation method is employed to obtain the second-harmonic correction term in the slip-stacking Hamiltonian. The Hamiltonian approach provides a clear optimal method for choosing the slip-stacking parameter and improving stacking efficiency. The dynamics are applied specifically to the Fermilab Booster-Recycler complex. As a result, the dynamics can also be applied to other accelerator complexes.
Lai, Chen-Yen; Chien, Chih-Chun
2016-01-01
While batteries offer electronic source and sink for electronic devices, atomic analogues of source and sink and their theoretical descriptions have been a challenge in cold-atom systems. Here we consider dynamically emerged local potentials as controllable source and sink for bosonic atoms. Although a sink potential can collect bosons in equilibrium and indicate its usefulness in the adiabatic limit, sudden switching of the potential exhibits low effectiveness in pushing bosons into it. This is due to conservation of energy and particle in isolated systems such as cold atoms. By varying the potential depth and interaction strength, the systems can further exhibit averse response, where a deeper emerged potential attracts less bosonic atoms into it. To explore possibilities for improving the effectiveness, we investigate what types of system-environment coupling can help bring bosons into a dynamically emerged sink, and a Lindblad operator corresponding to local cooling is found to serve the purpose. PMID:27849034
Lai, Chen-Yen; Chien, Chih-Chun
2016-11-16
While batteries offer electronic source and sink for electronic devices, atomic analogues of source and sink and their theoretical descriptions have been a challenge in cold-atom systems. Here we consider dynamically emerged local potentials as controllable source and sink for bosonic atoms. Although a sink potential can collect bosons in equilibrium and indicate its usefulness in the adiabatic limit, sudden switching of the potential exhibits low effectiveness in pushing bosons into it. This is due to conservation of energy and particle in isolated systems such as cold atoms. By varying the potential depth and interaction strength, the systems can further exhibit averse response, where a deeper emerged potential attracts less bosonic atoms into it. To explore possibilities for improving the effectiveness, we investigate what types of system-environment coupling can help bring bosons into a dynamically emerged sink, and a Lindblad operator corresponding to local cooling is found to serve the purpose.
NASA Astrophysics Data System (ADS)
Lai, Chen-Yen; Chien, Chih-Chun
2016-11-01
While batteries offer electronic source and sink for electronic devices, atomic analogues of source and sink and their theoretical descriptions have been a challenge in cold-atom systems. Here we consider dynamically emerged local potentials as controllable source and sink for bosonic atoms. Although a sink potential can collect bosons in equilibrium and indicate its usefulness in the adiabatic limit, sudden switching of the potential exhibits low effectiveness in pushing bosons into it. This is due to conservation of energy and particle in isolated systems such as cold atoms. By varying the potential depth and interaction strength, the systems can further exhibit averse response, where a deeper emerged potential attracts less bosonic atoms into it. To explore possibilities for improving the effectiveness, we investigate what types of system-environment coupling can help bring bosons into a dynamically emerged sink, and a Lindblad operator corresponding to local cooling is found to serve the purpose.
Teng, Yu; Kong, Nan; Tu, Wanzhu
2015-07-11
Chlamydia infection (CT) is one of the most commonly reported sexually transmitted diseases. It is often referred to as a "silent" disease with the majority of infected people having no symptoms. Without early detection, it can progress to serious reproductive and other health problems. Economical identification of asymptomatically infected is a key public health challenge. Increasing evidence suggests that CT infection risk varies over the range of adolescence. Hence, age-dependent screening strategies with more frequent testing for certain age groups of higher risk may be cost-saving in controlling the disease. We study the optimization of age-dependent screening strategies for population-based chlamydia infection screening among young women. We develop an age-structured compartment model for CT natural progress, screening, and treatment. We apply parameter optimization on the resultant PDE-based system dynamical models with the objective of minimizing the total care spending, including screening and treatment costs during the program period and anticipated costs of treating the sequelae afterwards). For ease of practical implementation, we also search for the best screening initiation age for strategies with a constant screening frequency. The optimal age-dependent strategies identified outperform the current CDC recommendations both in terms of total care spending and disease prevalence at the termination of the program. For example, the age-dependent strategy that allows monthly screening rate changes can save about 5% of the total spending. Our results suggest early initiation of CT screening is likely beneficial to the cost saving and prevalence reduction. Finally, our results imply that the strategy design may not be sensitive to accurate quantification of the age-specific CT infection risk if screening initiation age and screening rate are the only decisions to make. Our research demonstrates the potential economic benefit of age-dependent screening
NASA Technical Reports Server (NTRS)
Draper, Clara; Reichle, Rolf; De Lannoy, Gabrielle; Scarino, Benjamin
2015-01-01
In land data assimilation, bias in the observation-minus-forecast (O-F) residuals is typically removed from the observations prior to assimilation by rescaling the observations to have the same long-term mean (and higher-order moments) as the corresponding model forecasts. Such observation rescaling approaches require a long record of observed and forecast estimates, and an assumption that the O-F mean differences are stationary. A two-stage observation bias and state estimation filter is presented, as an alternative to observation rescaling that does not require a long data record or assume stationary O-F mean differences. The two-stage filter removes dynamic (nonstationary) estimates of the seasonal scale O-F mean difference from the assimilated observations, allowing the assimilation to correct the model for synoptic-scale errors without adverse effects from observation biases. The two-stage filter is demonstrated by assimilating geostationary skin temperature (Tsk) observations into the Catchment land surface model. Global maps of the O-F mean differences are presented, and the two-stage filter is evaluated for one year over the Americas. The two-stage filter effectively removed the Tsk O-F mean differences, for example the GOES-West O-F mean difference at 21:00 UTC was reduced from 5.1 K for a bias-blind assimilation to 0.3 K. Compared to independent in situ and remotely sensed Tsk observations, the two-stage assimilation reduced the unbiased Root Mean Square Difference (ubRMSD) of the modeled Tsk by 10 of the open-loop values.
Multiscale model approach for magnetization dynamics simulations
NASA Astrophysics Data System (ADS)
De Lucia, Andrea; Krüger, Benjamin; Tretiakov, Oleg A.; Kläui, Mathias
2016-11-01
Simulations of magnetization dynamics in a multiscale environment enable the rapid evaluation of the Landau-Lifshitz-Gilbert equation in a mesoscopic sample with nanoscopic accuracy in areas where such accuracy is required. We have developed a multiscale magnetization dynamics simulation approach that can be applied to large systems with spin structures that vary locally on small length scales. To implement this, the conventional micromagnetic simulation framework has been expanded to include a multiscale solving routine. The software selectively simulates different regions of a ferromagnetic sample according to the spin structures located within in order to employ a suitable discretization and use either a micromagnetic or an atomistic model. To demonstrate the validity of the multiscale approach, we simulate the spin wave transmission across the regions simulated with the two different models and different discretizations. We find that the interface between the regions is fully transparent for spin waves with frequency lower than a certain threshold set by the coarse scale micromagnetic model with no noticeable attenuation due to the interface between the models. As a comparison to exact analytical theory, we show that in a system with a Dzyaloshinskii-Moriya interaction leading to spin spirals, the simulated multiscale result is in good quantitative agreement with the analytical calculation.
NASA Technical Reports Server (NTRS)
Chen, W. E. W.; Hepler, W. A.; Yuan, S. W. K.; Frederking, T. H. K.
1985-01-01
Advanced dynamic insulation systems were analyzed from a thermodynamic point of view. A particular performance measure is proposed in order to characterize various insulations in a unique manner. This measure is related to a base quantity, the refrigeration power ratio. The latter is the minimum refrigeration power, for a particular dynamic insulation limit, to the actual reliquefaction power associated with cryoliquid boiloff. This ratio serves as reference quantity which is approximately constant for a specific ductless insulation at a chosen normal boiling point. Each real container with support structure, vent tube, and other transverse components requires a larger refrigeration power. The ratio of the actual experimental power to the theoretical value of the support-less system is a suitable measure of the entire insulation performance as far as parasitic heat leakage is concerned. The present characterization is illustrated using simple thermodynamic system examples including experiments with liquid nitrogen. Numerical values are presented and a comparison with liquid helium is given.
NASA Astrophysics Data System (ADS)
Chen, W. E. W.; Hepler, W. A.; Yuan, S. W. K.; Frederking, T. H. K.
1985-10-01
Advanced dynamic insulation systems were analyzed from a thermodynamic point of view. A particular performance measure is proposed in order to characterize various insulations in a unique manner. This measure is related to a base quantity, the refrigeration power ratio. The latter is the minimum refrigeration power, for a particular dynamic insulation limit, to the actual reliquefaction power associated with cryoliquid boiloff. This ratio serves as reference quantity which is approximately constant for a specific ductless insulation at a chosen normal boiling point. Each real container with support structure, vent tube, and other transverse components requires a larger refrigeration power. The ratio of the actual experimental power to the theoretical value of the support-less system is a suitable measure of the entire insulation performance as far as parasitic heat leakage is concerned. The present characterization is illustrated using simple thermodynamic system examples including experiments with liquid nitrogen. Numerical values are presented and a comparison with liquid helium is given.
NASA Technical Reports Server (NTRS)
Keith, Bruce; Ford, David N.; Horton, Radley M.
2016-01-01
The purpose of this study is to evaluate simulated fill rate scenarios for the Grand Ethiopian Renaissance Dam while taking into account plausible climate change outcomes for the Nile River Basin. The region lacks a comprehensive equitable water resource management strategy, which creates regional security concerns and future possible conflicts. We employ climate estimates from 33 general circulation models within a system dynamics model as a step in moving toward a feasible regional water resource management strategy. We find that annual reservoir fill rates of 8-15% are capable of building hydroelectric capacity in Ethiopia while concurrently ensuring a minimum level of stream flow disruption into Egypt before 2039. Insofar as climate change estimates suggest a modest average increase in stream flow into the Aswan, climate changes through 2039 are unlikely to affect the fill rate policies. However, larger fill rates will have a more detrimental effect on stream flow into the Aswan, particularly beyond a policy of 15%. While this study demonstrates that a technical solution for reservoir fill rates is feasible, the corresponding policy challenge is political. Implementation of water resource management strategies in the Nile River Basin specifically and Africa generally will necessitate a national and regional willingness to cooperate.
NASA Astrophysics Data System (ADS)
Abidin, Norhaslinda Zainal; Zaibidi, Nerda Zura; Zulkepli, Jafri Hj
2015-10-01
Obesity is a medical condition where an individual has an excessive amount of body fat. There are many factors contributing to obesity and one of them is the sedentary behaviour. Rapid development in industrialization and urbanization has brought changes to Malaysia's socioeconomic, especially the lifestyles of Malaysians. With this lifestyle transition, one of the impact is on weight and obesity. How does sedentary behaviour have an impact on the growth of Malaysian population's weight and obesity? What is the most effective sedentary behaviour preventing strategy to obesity? Is it through reduction in duration or frequency of sedentary behaviour? Thus, the aim of this paper is to design an intervention to analyse the effect of decreasing duration and frequency of sedentary behaviour on the population reversion trends of average weight (AW), average body mass index (ABMI), and prevalence of overweight and obesity (POVB). This study combines the different strands of sub-models comprised of nutrition, physical activity and body metabolism, and then synthesis these knowledge into a system dynamics of weight behaviour model, namely SIMULObese. Findings from this study revealed that Malaysian's adults spend a lot of time engaged in sedentary behaviour and this resulted in weight gain and obesity. Comparing between frequency and duration of sedentary behaviour, this study reported that reduced in duration or time spend in sedentary behaviour is a better preventing strategy to obesity compared to duration. As a summary, this study highlighted the importance of decreasing the frequency and duration of sedentary behaviour in developing guidelines to prevent obesity.
Salimi, Parisa; Hamedi, Mohsen; Jamshidi, Nima; Vismeh, Milad
2017-04-01
Diabetes and its associated complications are realized as one of the most challenging medical conditions threatening more than 29 million people only in the USA. The forecasts suggest a suffering of more than half a billion worldwide by 2030. Amid all diabetic complications, diabetic foot ulcer (DFU) has attracted much scientific investigations to lead to a better management of this disease. In this paper, a system thinking methodology is adopted to investigate the dynamic nature of the ulceration. The causal loop diagram as a tool is utilized to illustrate the well-researched relations and interrelations between causes of the DFU. The result of clustering causality evaluation suggests a vicious loop that relates external trauma to callus. Consequently a hypothesis is presented which localizes development of foot ulceration considering distribution of normal and shear stress. It specifies that normal and tangential forces, as the main representatives of external trauma, play the most important role in foot ulceration. The evaluation of this hypothesis suggests the significance of the information related to both normal and shear stress for managing DFU. The results also discusses how these two react on different locations on foot such as metatarsal head, heel and hallux. The findings of this study can facilitate tackling the complexity of DFU problem and looking for constructive mitigation measures. Moreover they lead to developing a more promising methodology for managing DFU including better prognosis, designing prosthesis and insoles for DFU and patient caring recommendations. Copyright © 2017 Elsevier Ltd. All rights reserved.
NASA Technical Reports Server (NTRS)
Keith, Bruce; Ford, David N.; Horton, Radley M.
2016-01-01
The purpose of this study is to evaluate simulated fill rate scenarios for the Grand Ethiopian Renaissance Dam while taking into account plausible climate change outcomes for the Nile River Basin. The region lacks a comprehensive equitable water resource management strategy, which creates regional security concerns and future possible conflicts. We employ climate estimates from 33 general circulation models within a system dynamics model as a step in moving toward a feasible regional water resource management strategy. We find that annual reservoir fill rates of 8-15% are capable of building hydroelectric capacity in Ethiopia while concurrently ensuring a minimum level of stream flow disruption into Egypt before 2039. Insofar as climate change estimates suggest a modest average increase in stream flow into the Aswan, climate changes through 2039 are unlikely to affect the fill rate policies. However, larger fill rates will have a more detrimental effect on stream flow into the Aswan, particularly beyond a policy of 15%. While this study demonstrates that a technical solution for reservoir fill rates is feasible, the corresponding policy challenge is political. Implementation of water resource management strategies in the Nile River Basin specifically and Africa generally will necessitate a national and regional willingness to cooperate.
NASA Astrophysics Data System (ADS)
Mechal, Abraham; Birk, Steffen; Dietzel, Martin; Leis, Albrecht; Winkler, Gerfried; Mogessie, Aberra; Kebede, Seifu
2017-03-01
Hydrochemical and isotope data in conjunction with hydraulic head and spring discharge observations were used to characterize the regional groundwater flow dynamics and the role of the tectonic setting in the Gidabo River Basin, Ethiopian Rift. Both groundwater levels and hydrochemical and isotopic data indicate groundwater flow from the major recharge area in the highland and escarpment into deep rift floor aquifers, suggesting a deep regional flow system can be distinguished from the shallow local aquifers. The δ18O and δ2H values of deep thermal (≥30 °C) groundwater are depleted relative to the shallow (<60 m below ground level) groundwater in the rift floor. Based on the δ18O values, the thermal groundwater is found to be recharged in the highland around 2,600 m a.s.l. and on average mixed with a proportion of 30 % shallow groundwater. While most groundwater samples display diluted solutions, δ13C data of dissolved inorganic carbon reveal that locally the thermal groundwater near fault zones is loaded with mantle CO2, which enhances silicate weathering and leads to anomalously high total dissolved solids (2,000-2,320 mg/l) and fluoride concentrations (6-15 mg/l) exceeding the recommended guideline value. The faults are generally found to act as complex conduit leaky barrier systems favoring vertical mixing processes. Normal faults dipping to the west appear to facilitate movement of groundwater into deeper aquifers and towards the rift floor, whereas those dipping to the east tend to act as leaky barriers perpendicular to the fault but enable preferential flow parallel to the fault plane.
Single timepoint models of dynamic systems
Sachs, K.; Itani, S.; Fitzgerald, J.; Schoeberl, B.; Nolan, G. P.; Tomlin, C. J.
2013-01-01
Many interesting studies aimed at elucidating the connectivity structure of biomolecular pathways make use of abundance measurements, and employ statistical and information theoretic approaches to assess connectivities. These studies often do not address the effects of the dynamics of the underlying biological system, yet dynamics give rise to impactful issues such as timepoint selection and its effect on structure recovery. In this work, we study conditions for reliable retrieval of the connectivity structure of a dynamic system, and the impact of dynamics on structure-learning efforts. We encounter an unexpected problem not previously described in elucidating connectivity structure from dynamic systems, show how this confounds structure learning of the system and discuss possible approaches to overcome the confounding effect. Finally, we test our hypotheses on an accurate dynamic model of the IGF signalling pathway. We use two structure-learning methods at four time points to contrast the performance and robustness of those methods in terms of recovering correct connectivity. PMID:24511382
NASA Astrophysics Data System (ADS)
Barraco, A.; Cuny, B.; Ishiomin, G.
Analytical techniques for dynamic modeling of mechanical systems with deformable members are developed and demonstrated. Formulations for the rigid member and the flexible member are derived; the position of an arbitrary point is defined; and the construction of the complete model from these components is explained. Numerical results for the case of a planar four-bar parallelogram rotating about a fixed axis located in the same plane are presented in graphs and discussed.
1976-07-30
I, Academic Press, pp. 211-222, 1976. [24] LASALLE , J.P. (with E.N. Onwuchekwa) An Invariance Principle for Vector Liapunov Functions. Dynamical...Press, Inc. pp. XVii-XXi, 1976. V-7 [59] LASALLE , J.P. Stability Theory and Invariance Principles . Chapter 5: Topological Dynamtical Systems...to extend the earlier work of Hurt in [50] in applying the invariance principle to extend Liapunov’s direct method. An exposition of some of these
NASA Technical Reports Server (NTRS)
Wisdom, Jack
2002-01-01
In these 18 years, the research has touched every major dynamical problem in the solar system, including: the effect of chaotic zones on the distribution of asteroids, the delivery of meteorites along chaotic pathways, the chaotic motion of Pluto, the chaotic motion of the outer planets and that of the whole solar system, the delivery of short period comets from the Kuiper belt, the tidal evolution of the Uranian arid Galilean satellites, the chaotic tumbling of Hyperion and other irregular satellites, the large chaotic variations of the obliquity of Mars, the evolution of the Earth-Moon system, and the resonant core- mantle dynamics of Earth and Venus. It has introduced new analytical and numerical tools that are in widespread use. Today, nearly every long-term integration of our solar system, its subsystems, and other solar systems uses algorithms that was invented. This research has all been primarily Supported by this sequence of PGG NASA grants. During this period published major investigations of tidal evolution of the Earth-Moon system and of the passage of the Earth and Venus through non-linear core-mantle resonances were completed. It has published a major innovation in symplectic algorithms: the symplectic corrector. A paper was completed on non-perturbative hydrostatic equilibrium.
Bam, L; McLaren, Z M; Coetzee, E; von Leipzig, K H
2017-10-01
The under-performance of supply chains presents a significant hindrance to disease control in developing countries. Stock-outs of essential medicines lead to treatment interruption which can force changes in patient drug regimens, drive drug resistance and increase mortality. This study is one of few to quantitatively evaluate the effectiveness of supply chain policies in reducing shortages and costs. This study develops a systems dynamics simulation model of the downstream supply chain for amikacin, a second-line tuberculosis drug using 10 years of South African data. We evaluate current supply chain performance in terms of reliability, responsiveness and agility, following the widely-used Supply Chain Operation Reference framework. We simulate 141 scenarios that represent different combinations of supplier characteristics, inventory management strategies and demand forecasting methods to identify the Pareto optimal set of management policies that jointly minimize the number of shortages and total cost. Despite long supplier lead times and unpredictable demand, the amikacin supply chain is 98% reliable and agile enough to accommodate a 20% increase in demand without a shortage. However, this is accomplished by overstocking amikacin by 167%, which incurs high holding costs. The responsiveness of suppliers is low: only 57% of orders are delivered to the central provincial drug depot within one month. We identify three Pareto optimal safety stock management policies. Short supplier lead time can produce Pareto optimal outcomes even in the absence of other optimal policies. This study produces concrete, actionable guidelines to cost-effectively reduce stock-outs by implementing optimal supply chain policies. Preferentially selecting drug suppliers with short lead times accommodates unexpected changes in demand. Optimal supply chain management should be an essential component of national policy to reduce the mortality rate. © The Author 2017. Published by Oxford
Nägele, Thomas; Kandel, Benjamin A; Frana, Sabine; Meissner, Meike; Heyer, Arnd G
2011-02-01
Low temperature is an important environmental factor affecting the performance and distribution of plants. During the so-called process of cold acclimation, many plants are able to develop low-temperature tolerance, associated with the reprogramming of a large part of their metabolism. In this study, we present a systems biology approach based on mathematical modelling to determine interactions between the reprogramming of central carbohydrate metabolism and the development of freezing tolerance in two accessions of Arabidopsis thaliana. Different regulation strategies were observed for (a) photosynthesis, (b) soluble carbohydrate metabolism and (c) enzyme activities of central metabolite interconversions. Metabolism of the storage compound starch was found to be independent of accession-specific reprogramming of soluble sugar metabolism in the cold. Mathematical modelling and simulation of cold-induced metabolic reprogramming indicated major differences in the rates of interconversion between the pools of hexoses and sucrose, as well as the rate of assimilate export to sink organs. A comprehensive overview of interconversion rates is presented, from which accession-specific regulation strategies during exposure to low temperature can be derived. We propose this concept as a tool for predicting metabolic engineering strategies to optimize plant freezing tolerance. We confirm that a significant improvement in freezing tolerance in plants involves multiple regulatory instances in sucrose metabolism, and provide evidence for a pivotal role of sucrose-hexose interconversion in increasing the cold acclimation output. © 2010 The Authors Journal compilation © 2010 FEBS.
Dynamically controlled crystal growth system
NASA Technical Reports Server (NTRS)
Bray, Terry L. (Inventor); Kim, Larry J. (Inventor); Harrington, Michael (Inventor); DeLucas, Lawrence J. (Inventor)
2002-01-01
Crystal growth can be initiated and controlled by dynamically controlled vapor diffusion or temperature change. In one aspect, the present invention uses a precisely controlled vapor diffusion approach to monitor and control protein crystal growth. The system utilizes a humidity sensor and various interfaces under computer control to effect virtually any evaporation rate from a number of different growth solutions simultaneously by means of an evaporative gas flow. A static laser light scattering sensor can be used to detect aggregation events and trigger a change in the evaporation rate for a growth solution. A control/follower configuration can be used to actively monitor one chamber and accurately control replicate chambers relative to the control chamber. In a second aspect, the invention exploits the varying solubility of proteins versus temperature to control the growth of protein crystals. This system contains miniature thermoelectric devices under microcomputer control that change temperature as needed to grow crystals of a given protein. Complex temperature ramps are possible using this approach. A static laser light scattering probe also can be used in this system as a non-invasive probe for detection of aggregation events. The automated dynamic control system provides systematic and predictable responses with regard to crystal size. These systems can be used for microgravity crystallization projects, for example in a space shuttle, and for crystallization work under terrestial conditions. The present invention is particularly useful for macromolecular crystallization, e.g. for proteins, polypeptides, nucleic acids, viruses and virus particles.
ERIC Educational Resources Information Center
WIENS, JACOB H.
TO PERMIT COMPARATIVE ANALYSIS FOR PURPOSES OF EDUCATIONAL PLANNING AT SAN MATEO, FIVE INSTITUTIONS WITH SYSTEMS PROGRAMS ARE EVALUATED ON THE BASIS OF TRIP NOTES. OAKLAND COMMUNITY COLLEGE HAS BEEN COMPLETELY ORGANIZED AROUND THE VOLUNTARY WORK-STUDY LABORATORY APPROACH TO LEARNING. ORAL ROBERTS UNIVERSITY, OKLAHOMA CHRISTIAN COLLEGE, HENRY FORD…
A Systems Approach to School Counseling.
ERIC Educational Resources Information Center
Carns, Ann W.; Carns, Michael R.
1997-01-01
Argues that the use of systems counseling in the public school offers advantages for the school counselor. Explores the theoretical framework of systems counseling, such as family dynamics and homeostasis. Provides a case study as seen through a systems perspective to illustrate a systems approach. Gives implications for counselors. (RJM)
A Systems Approach to School Counseling.
ERIC Educational Resources Information Center
Carns, Ann W.; Carns, Michael R.
1997-01-01
Argues that the use of systems counseling in the public school offers advantages for the school counselor. Explores the theoretical framework of systems counseling, such as family dynamics and homeostasis. Provides a case study as seen through a systems perspective to illustrate a systems approach. Gives implications for counselors. (RJM)
Cooperative Autonomic Management in Dynamic Distributed Systems
NASA Astrophysics Data System (ADS)
Xu, Jing; Zhao, Ming; Fortes, José A. B.
The centralized management of large distributed systems is often impractical, particularly when the both the topology and status of the system change dynamically. This paper proposes an approach to application-centric self-management in large distributed systems consisting of a collection of autonomic components that join and leave the system dynamically. Cooperative autonomic components self-organize into a dynamically created overlay network. Through local information sharing with neighbors, each component gains access to global information as needed for optimizing performance of applications. The approach has been validated and evaluated by developing a decentralized autonomic system consisting of multiple autonomic application managers previously developed for the In-VIGO grid-computing system. Using analytical results from complex random network and measurements done in a prototype system, we demonstrate the robustness, self-organization and adaptability of our approach, both theoretically and experimentally.
NASA Astrophysics Data System (ADS)
Shu, S.; Hoffman, F. M.; Kumar, J.; Hargrove, W. W.; Jain, A. K.
2014-12-01
Uncertainties in data retrieved from remote sensor present challenges to using such observational products to constrain Earth system model (ESM) results. While simple statistics can be applied to compare models with observations, advanced data mining methods, like unsupervised cluster analysis, offer powerful tools for summarizing model-data differences in the spatial and temporal patterns of ecological characteristics. We compared modeled land surface phenology with MODIS 16-day composited Normalized Difference Vegetation Index (NDVI) (MOD13C1) and Global Inventory Modeling and Mapping Studies (GIMMS) NDVI3g products spanning years 2001 to 2012. Annual traces of NDVI from two ESMs (CESM-CLM and ISAM) were calculated using modeled radiation from the output of historical simulations and corrected to better match observed properties by considering instrumental bandwidths and solar angle. Multivariate Spatio-Temporal Clustering (MSTC) was applied to annual traces of MODIS and GIMMS NDVI to create phenological regions (phenoregions) and analyzed using Mapcurves, a tool designed for comparing categorical maps, to check the consistency of the spatial patterns of observations before assessing model output. To evaluate modeled phenology, MSTC was first applied to obtain representative centroids of modeled NDVI and separately of satellite NDVI. The Mapcurves method was applied to compare the spatial patterns of modeled phenology to remote sensing observations. Next, modeled NDVI were projected onto the centroids defining phenoregions of observed NDVI, and observed NDVI were projected onto the centroids of modeled NDVI. Mapcurves was then applied to compare the spatial patterns of these classifications. Results showed a general agreement in the spatial pattern of phenoregions from models to satellite observations, except in high-latitude regions and agricultural areas. MSTC averages out small deviations between modeled and observed phenology, which are exhibited across all
Approaches for modeling magnetic nanoparticle dynamics
Reeves, Daniel B; Weaver, John B
2014-01-01
Magnetic nanoparticles are useful biological probes as well as therapeutic agents. There have been several approaches used to model nanoparticle magnetization dynamics for both Brownian as well as Néel rotation. The magnetizations are often of interest and can be compared with experimental results. Here we summarize these approaches including the Stoner-Wohlfarth approach, and stochastic approaches including thermal fluctuations. Non-equilibrium related temperature effects can be described by a distribution function approach (Fokker-Planck equation) or a stochastic differential equation (Langevin equation). Approximate models in several regimes can be derived from these general approaches to simplify implementation. PMID:25271360
Coarsening in dynamical systems
NASA Astrophysics Data System (ADS)
Manuca, Radu
1997-11-01
The way in which the description of a physical system changes when viewed on different length or time scales is an important characteristic of that system. The present work studies the effects of coarsening the description (i.e. changing the spatial or temporal observation scale) of dynamical systems at various levels. First, the effects of spatial coarsening on the equations of motion are analyzed for the Kuramoto-Sivashinsky equation. The linearized equation is used to evaluate the stability of arbitrary solutions under perturbations and extract the Lyapunov exponents and some properties of the power spectrum. Second, the effects of time or spatial coarsening on the integral solutions are analyzed for some high Reynolds number Couette-Taylor turbulence experiments and for numerical simulations of the Kuramoto-Sivashinsky equation. Quantities related to metric entropies are shown to scale with the observation scale for these systems. Third, a new method of time coarsening in nonstationary systems is presented. Nonstationary effects are examined on a ball-bearing experiment and on epileptic EEG recordings. Finally, the coarsening of a very complex state space describing the configuration of a factory floor is presented. By introducing global degrees of freedom, the complexity of the representation of the system is highly reduced, without significant information loss. The methods presented here are nonstandard, but they share with the classical methods the goal of replacing the complex description of a system with a much simpler, but relevant one.
Parallelized implementation of dynamical particle system
NASA Astrophysics Data System (ADS)
Mašek, Jan; Frantík, Petr; Vořechovský, Miroslav
2017-07-01
The paper presents approaches to implementation of solution of discrete dynamical system of mutually repelling particles. Two platforms: a single-thread JAVA process and parallelized CUDA C solution, are employed for the dynamical simulation. Qualities of both platforms are discussed and explained as their performance when solving two proposed interaction laws is compared.
An Ecological Approach to Learning Dynamics
ERIC Educational Resources Information Center
Normak, Peeter; Pata, Kai; Kaipainen, Mauri
2012-01-01
New approaches to emergent learner-directed learning design can be strengthened with a theoretical framework that considers learning as a dynamic process. We propose an approach that models a learning process using a set of spatial concepts: learning space, position of a learner, niche, perspective, step, path, direction of a step and step…
Lee, Lynette; Heffernan, Mark; McDonnell, Geoffrey; Short, Stephanie D; Naganathan, Vasi
2016-06-01
Objective The aims of this study were to estimate the prevalence count of people with intellectual developmental disorders (IDD) in New South Wales (NSW) in 2003, by age groups, and to forecast their prevalence until 2043. Methods Administrative data obtained from NSW government departments of education, pensions, health and disability were used to profile the number of people whose characteristics met the criteria for 'intellectual developmental disorders' who had received services in 2003. These figures were compared with published tables of NSW data from the national self-report Survey of Disability, Ageing and Carers (SDAC) of 2003 to estimate the likely prevalence of people with intellectual developmental disorders, by age groups in that year. The results were then used as baseline figures in a computational system dynamics model of the aging chain of people with these disorders, built to project prevalence to 2043. Results The number of people who met the criteria for having intellectual developmental disorder in NSW in 2003 was estimated to be 57000 (a ratio of 85 per 10000), with 32000 aged 0-15 years, 15000 aged 16-39 years, 9000 aged 40-64 years and 1000 aged 65+ years. Using these figures as baseline, the computer simulation predicted a total increase to 77225 people in 2013 and 135905 people by 2043. By 2043, the number of children with intellectual developmental disorders will have doubled, from 32000 to 59480, and the number of adults will have tripled, from 25000 to 76420. Conclusions This modelling technique forecast an increase in the prevalence count of people with intellectual developmental disorders in NSW over the period 2003-43 from 57000 (85 per 10000) to 135905 (135 per 10000). These predictions may have important implications for the planning of specialist health services for this group of people. What is known about the topic? The prevalence ratio of people with intellectual developmental disorders is quoted at lying between 1% and 2% of
Kaushik, Aman Chandra; Sahi, Shakti
2015-06-01
Systems biology addresses challenges in the analysis of genomics data, especially for complex genes and protein interactions using Meta data approach on various signaling pathways. In this paper, we report systems biology and biological circuits approach to construct pathway and identify early gene and protein interactions for predicting GPR142 responses in Type 2 diabetes. The information regarding genes, proteins and other molecules involved in Type 2 diabetes were retrieved from literature and kinetic simulation of GPR142 was carried out in order to determine the dynamic interactions. The major objective of this work was to design a GPR142 biochemical pathway using both systems biology as well as biological circuits synthetically. The term 'synthetically' refers to building biological circuits for cell signaling pathway especially for hormonal pathway disease. The focus of the paper is on logical components and logical circuits whereby using these applications users can create complex virtual circuits. Logic gates process represents only true or false and investigates whether biological regulatory circuits are active or inactive. The basic gates used are AND, NAND, OR, XOR and NOT gates and Integrated circuit composition of many such basic gates and some derived gates. Biological circuits may have a futuristic application in biomedical sciences which may involve placing a micro chip in human cells to modulate the down or up regulation of hormonal disease.
NASA Astrophysics Data System (ADS)
Sankovich, Vladimir
1998-12-01
The goal of this paper is to build a consistent physical theory of the dynamics of the bat-ball interaction. This requires creating realistic models for both the softball bat and the softball. Some of the features of these models are known phenomenologically, from experiments conducted in our laboratory, others will be introduced and computed from first principles here for the first time. Both interacting objects are treated from the viewpoint of the theory of elasticity, and it is shown how a computer can be used to accurately calculate all the relevant characteristics of batball collisions. It is shown also how the major elastic parameters of the material constituting the interior of a softball can be determined using the existing experimental data. These parameters, such as the Young's modulus, the Poisson ratio and the damping coefficient are vital for the accurate description of the ball's dynamics. We are demonstrating how the existing theories of the elastic behavior of solid bars and hollow shells can be augmented to simplify the resulting equations and make the subsequent computer analysis feasible. The standard system of fourth-order PDE's is reduced to a system of the second order, because of the inclusion of the usually ignored effects of the shear forces in the bat.
Data Systems Dynamic Simulator
NASA Technical Reports Server (NTRS)
Rouff, Christopher; Clark, Melana; Davenport, Bill; Message, Philip
1993-01-01
The Data System Dynamic Simulator (DSDS) is a discrete event simulation tool. It was developed for NASA for the specific purpose of evaluating candidate architectures for data systems of the Space Station era. DSDS provides three methods for meeting this requirement. First, the user has access to a library of standard pre-programmed elements. These elements represent tailorable components of NASA data systems and can be connected in any logical manner. Secondly, DSDS supports the development of additional elements. This allows the more sophisticated DSDS user the option of extending the standard element set. Thirdly, DSDS supports the use of data streams simulation. Data streams is the name given to a technique that ignores packet boundaries, but is sensitive to rate changes. Because rate changes are rare compared to packet arrivals in a typical NASA data system, data stream simulations require a fraction of the CPU run time. Additionally, the data stream technique is considerably more accurate than another commonly-used optimization technique.
Trani, Jean-Francois; Ballard, Ellis; Bakhshi, Parul; Hovmand, Peter
2016-01-01
Afghanistan lacks suitable specialized mental healthcare services despite high prevalence of severe mental health disorders which are aggravated by the conflict and numerous daily stressors. Recent studies have shown that Afghans with mental illness are not only deprived of care but are vulnerable in many other ways. Innovative participatory approaches to the design of mental healthcare policies and programs are needed in such challenging context. We employed community based system dynamics to examine interactions between multiple factors and actors to examine the problem of persistently low service utilization for people with mental illness. Group model building sessions, designed based on a series of scripts and led by three facilitators, took place with NGO staff members in Mazar-I-Sharif in July 2014 and in Kabul in February 2015. We identified major feedback loops that constitute a hypothesis of how system components interact to generate a persistently low rate of service utilization by people with mental illness. In particular, we found that the interaction of the combined burdens of poverty and cost of treatment interact with cultural and social stigmatizing beliefs, in the context of limited clinical or other treatment support, to perpetuate low access to care for people with mental disorders. These findings indicate that the introduction of mental healthcare services alone will not be sufficient to meaningfully improve the condition of individuals with mental illness if community stigma and poverty are not addressed concurrently. Our model highlights important factors that prevent persons with mental illness from accessing services. Our study demonstrates that group model building methods using community based system dynamics can provide an effective tool to elicit a common vision on a complex problem and identify shared potential strategies for intervention in a development and global health context. Its strength and originality is the leadership role
NASA Astrophysics Data System (ADS)
Alexandridis, Konstantinos T.
This dissertation adopts a holistic and detailed approach to modeling spatially explicit agent-based artificial intelligent systems, using the Multi Agent-based Behavioral Economic Landscape (MABEL) model. The research questions that addresses stem from the need to understand and analyze the real-world patterns and dynamics of land use change from a coupled human-environmental systems perspective. Describes the systemic, mathematical, statistical, socio-economic and spatial dynamics of the MABEL modeling framework, and provides a wide array of cross-disciplinary modeling applications within the research, decision-making and policy domains. Establishes the symbolic properties of the MABEL model as a Markov decision process, analyzes the decision-theoretic utility and optimization attributes of agents towards comprising statistically and spatially optimal policies and actions, and explores the probabilogic character of the agents' decision-making and inference mechanisms via the use of Bayesian belief and decision networks. Develops and describes a Monte Carlo methodology for experimental replications of agent's decisions regarding complex spatial parcel acquisition and learning. Recognizes the gap on spatially-explicit accuracy assessment techniques for complex spatial models, and proposes an ensemble of statistical tools designed to address this problem. Advanced information assessment techniques such as the Receiver-Operator Characteristic curve, the impurity entropy and Gini functions, and the Bayesian classification functions are proposed. The theoretical foundation for modular Bayesian inference in spatially-explicit multi-agent artificial intelligent systems, and the ensembles of cognitive and scenario assessment modular tools build for the MABEL model are provided. Emphasizes the modularity and robustness as valuable qualitative modeling attributes, and examines the role of robust intelligent modeling as a tool for improving policy-decisions related to land
Analysis of uterine contractions: a dynamical approach.
Nagarajan, R; Eswaran, H; Wilson, J D; Murphy, P; Lowery, C; Preissl, H
2003-07-01
The development of suitable techniques for quantifying mechanical and electrophysiological aspects of uterine contractions has been an active area of research. The uterus is a physiological system consisting of a large number of interacting muscle cells. The activity of these cells evolves with time, a trait characteristic of a dynamical system. While such complex physiological systems are non-linear by their very nature, whether this non-linearity is exhibited in the external recording is far from trivial. Traditional techniques such as spectral analysis have been used in the past, but these techniques implicitly assume that the process generating the contractions is linear and hence may be biased. In this tutorial review, a systematic approach using a hierarchy of surrogate algorithms is used to determine the nature of the process generating the contractions produced during labor. The results reveal that uterine contractions are probably generated by non-linear processes. The contraction segments were obtained through simultaneous recordings of the electrical and magnetic signals corresponding to the electrophysiological activity of the uterus and then analyzed. The electrical activity was recorded by placement of non-invasive electrodes onto the maternal abdomen and magnetic activity was recorded non-invasively using a superconducting quantum interference device (SQUID).
A macroscopic approach to glacier dynamics
Harrison, W.D.; Raymond, C.F.; Echelmeyer, K.A.; Krimmel, R.M.
2003-01-01
A simple approach to glacier dynamics is explored in which there is postulated to be a relationship between area and volume with three parameters: the time for area to respond to changes in volume, a thickness scale, and an area characterizing the condition of the initial state. This approach gives a good fit to the measurements of cumulative balance and area on South Cascade Glacier from 1970-97; the area time-scale is roughly 8 years, the thickness scale about 123 m, and the 1970 area roughly 4% larger than required for adjustment with volume. Combining this relationship with a version of mass continuity expressed in terms of area and volume produces a theory of glacier area and volume response to climate in which another time constant, the volume time-scale, appears. Area and volume both respond like a damped spring and mass system. The damping of the South Cascade response is approximately critical, and the volume time-scale is roughly 48 years, six times the area time-scale. The critically damped spring and mass analogy reproduces the time dependence predicted by the more complicated traditional theory of Nye.
The Feldenkrais Method: A Dynamic Approach to Changing Motor Behavior.
ERIC Educational Resources Information Center
Buchanan, Patricia A.; Ulrich, Beverly D.
2001-01-01
Describes the Feldenkrais Method of somatic education, noting parallels with a dynamic systems theory (DST) approach to motor behavior. Feldenkrais uses movement and perception to foster individualized improvement in function. DST explains that a human-environment system continually adapts to changing conditions and assembles behaviors…
Approaches for Resolving Dynamic IP Addressing.
ERIC Educational Resources Information Center
Foo, Schubert; Hui, Siu Cheung; Yip, See Wai; He, Yulan
1997-01-01
A problem with dynamic Internet protocol (IP) addressing arises when the Internet connection is through an Internet provider since the IP address is allocated only at connection time. This article examines a number of online and offline methods for resolving the problem. Suggests dynamic domain name system (DNS) and directory service look-up are…
Approaches for Resolving Dynamic IP Addressing.
ERIC Educational Resources Information Center
Foo, Schubert; Hui, Siu Cheung; Yip, See Wai; He, Yulan
1997-01-01
A problem with dynamic Internet protocol (IP) addressing arises when the Internet connection is through an Internet provider since the IP address is allocated only at connection time. This article examines a number of online and offline methods for resolving the problem. Suggests dynamic domain name system (DNS) and directory service look-up are…
1974-05-01
wm^^mrmm JlilJJLUJJ.l, UM *•* ". «^^~mw^-r mmmmmmmem DYNAMIC COLOR SCANNER SYSTEM L. T. Hunkler ITT Aerospaco/Gpticai Division S Fort Wayne ...Division, a division of International Telephone and Tele- graph Corporation, Fort Wayne , Indiana, under contract F33615-72- C-2071 for research and...iliKriiBiröfiiii-1, ■ ^ii ■"»*-—™""tWi "!—i^^^P«^ ^3 <o lil r^ ■ i u o o 0) (0 n •H Q (U ri 0) l-i 3 tP •H 20 SO-Z^H •— ■■■■I
Identification of dynamic systems, theory and formulation
NASA Technical Reports Server (NTRS)
Maine, R. E.; Iliff, K. W.
1985-01-01
The problem of estimating parameters of dynamic systems is addressed in order to present the theoretical basis of system identification and parameter estimation in a manner that is complete and rigorous, yet understandable with minimal prerequisites. Maximum likelihood and related estimators are highlighted. The approach used requires familiarity with calculus, linear algebra, and probability, but does not require knowledge of stochastic processes or functional analysis. The treatment emphasizes unification of the various areas in estimation in dynamic systems is treated as a direct outgrowth of the static system theory. Topics covered include basic concepts and definitions; numerical optimization methods; probability; statistical estimators; estimation in static systems; stochastic processes; state estimation in dynamic systems; output error, filter error, and equation error methods of parameter estimation in dynamic systems, and the accuracy of the estimates.
Xu, Zhijie; Meakin, Paul
2009-06-21
Dissipative particle dynamics (DPD) is an effective mesoscopic particle model with a lower computational cost than molecular dynamics because of the soft potentials that it employs. However, the soft potential is not strong enough to prevent the DPD particles that are used to represent the fluid from penetrating solid boundaries represented by stationary DPD particles. A phase-field variable, phi(x,t), is used to indicate the phase at point x and time t, with a smooth transition from -1 (phase 1) to +1 (phase 2) across the interface. We describe an efficient implementation of no-slip boundary conditions in DPD models that combines solid-liquid particle-particle interactions with reflection at a sharp boundary located with subgrid scale accuracy using the phase field. This approach can be used for arbitrarily complex flow geometries and other similar particle models (such as smoothed particle hydrodynamics), and the validity of the model is demonstrated by DPD simulations of flow in confined systems with various geometries.
NASA Astrophysics Data System (ADS)
Bleibel, Johannes; Domínguez, Alvaro; Oettel, Martin
2016-06-01
We build on an existing approximation scheme to the Smoluchowski equation in order to derive a dynamic density functional theory (DDFT) including two-body hydrodynamic interactions. A generalized diffusion equation and a wavenumber-dependent diffusion coefficient D(k) are derived by linearization in the density fluctuations. The result is applied to a colloidal monolayer at a fluid interface, having bulk-like hydrodynamic interactions and/or interacting via long-ranged capillary forces. In these cases, D(k) shows characteristic singularities as k\\to 0 . The consequences of these singularities are studied by means of analytical perturbation theory, numerical solution of DDFT and simulations for an explicit example: the capillary collapse of a finite, disk-like distribution of particles. There is in general a good agreement between DDFT and simulations if the initial density distributions for the theoretical prediction correspond to the actual initial configurations of simulations, rather than to an average over them. Otherwise, discrepancies arise that are discussed in detail.
Dynamic Modeling of ALS Systems
NASA Technical Reports Server (NTRS)
Jones, Harry
2002-01-01
The purpose of dynamic modeling and simulation of Advanced Life Support (ALS) systems is to help design them. Static steady state systems analysis provides basic information and is necessary to guide dynamic modeling, but static analysis is not sufficient to design and compare systems. ALS systems must respond to external input variations and internal off-nominal behavior. Buffer sizing, resupply scheduling, failure response, and control system design are aspects of dynamic system design. We develop two dynamic mass flow models and use them in simulations to evaluate systems issues, optimize designs, and make system design trades. One model is of nitrogen leakage in the space station, the other is of a waste processor failure in a regenerative life support system. Most systems analyses are concerned with optimizing the cost/benefit of a system at its nominal steady-state operating point. ALS analysis must go beyond the static steady state to include dynamic system design. All life support systems exhibit behavior that varies over time. ALS systems must respond to equipment operating cycles, repair schedules, and occasional off-nominal behavior or malfunctions. Biological components, such as bioreactors, composters, and food plant growth chambers, usually have operating cycles or other complex time behavior. Buffer sizes, material stocks, and resupply rates determine dynamic system behavior and directly affect system mass and cost. Dynamic simulation is needed to avoid the extremes of costly over-design of buffers and material reserves or system failure due to insufficient buffers and lack of stored material.
Dynamic focusing approach to mixed-level simulation
NASA Astrophysics Data System (ADS)
Fall, Thomas C.
1997-06-01
The dynamic focusing approach (DFA) has been under development for several years. Its intent is to address several of the issues of mixed level simulations, particularly the aggregational issues. Though the approach requires that the system be able to be modeled within certain constraints, many systems of interest fit well within them. This approach combines a hierarchical representation of knowledge with a stochastic propagation mechanism; this provides capability to gracefully move from coarse granularity to fine granularity under user guidance. Prototype tools have been developed for engineering analysis, combat simulation and TQM process implementation. This paper gives an overview of the approach and its current status.
ERIC Educational Resources Information Center
Grammatikopoulos, Vasilis
2012-01-01
The current study attempts to integrate parts of program theory and systems-based procedures in educational program evaluation. The educational program that was implemented, called the "Early Steps" project, proposed that physical education can contribute to various educational goals apart from the usual motor skills improvement. Basic…
ERIC Educational Resources Information Center
Grammatikopoulos, Vasilis
2012-01-01
The current study attempts to integrate parts of program theory and systems-based procedures in educational program evaluation. The educational program that was implemented, called the "Early Steps" project, proposed that physical education can contribute to various educational goals apart from the usual motor skills improvement. Basic…
Dynamics and kinematics of simple neural systems
Rabinovich, M. |; Selverston, A.; Rubchinsky, L.; Huerta, R.
1996-09-01
The dynamics of simple neural systems is of interest to both biologists and physicists. One of the possible roles of such systems is the production of rhythmic patterns, and their alterations (modification of behavior, processing of sensory information, adaptation, control). In this paper, the neural systems are considered as a subject of modeling by the dynamical systems approach. In particular, we analyze how a stable, ordinary behavior of a small neural system can be described by simple finite automata models, and how more complicated dynamical systems modeling can be used. The approach is illustrated by biological and numerical examples: experiments with and numerical simulations of the stomatogastric central pattern generators network of the California spiny lobster. {copyright} {ital 1996 American Institute of Physics.}
Systemic approaches to biodegradation.
Trigo, Almudena; Valencia, Alfonso; Cases, Ildefonso
2009-01-01
Biodegradation, the ability of microorganisms to remove complex chemicals from the environment, is a multifaceted process in which many biotic and abiotic factors are implicated. The recent accumulation of knowledge about the biochemistry and genetics of the biodegradation process, and its categorization and formalization in structured databases, has recently opened the door to systems biology approaches, where the interactions of the involved parts are the main subject of study, and the system is analysed as a whole. The global analysis of the biodegradation metabolic network is beginning to produce knowledge about its structure, behaviour and evolution, such as its free-scale structure or its intrinsic robustness. Moreover, these approaches are also developing into useful tools such as predictors for compounds' degradability or the assisted design of artificial pathways. However, it is the environmental application of high-throughput technologies from the genomics, metagenomics, proteomics and metabolomics that harbours the most promising opportunities to understand the biodegradation process, and at the same time poses tremendous challenges from the data management and data mining point of view.
Jin, Jinshuang; Welack, Sven; Luo, JunYan; Li, Xin-Qi; Cui, Ping; Xu, Rui-Xue; Yan, YiJing
2007-04-07
A hierarchical equations of motion formalism for a quantum dissipation system in a grand canonical bath ensemble surrounding is constructed on the basis of the calculus-on-path-integral algorithm, together with the parametrization of arbitrary non-Markovian bath that satisfies fluctuation-dissipation theorem. The influence functionals for both the fermion or boson bath interaction are found to be of the same path integral expression as the canonical bath, assuming they all satisfy the Gaussian statistics. However, the equation of motion formalism is different due to the fluctuation-dissipation theories that are distinct and used explicitly. The implications of the present work to quantum transport through molecular wires and electron transfer in complex molecular systems are discussed.
1995-12-01
conventional treatment plants " are: "Constructed wetland systems (1) are relatively inexpensive to construct and operate; (2) are easy to maintain; (3) provide... macrophytes are divided into free floating and rooted forms. The rooted forms are further subdivided into emergent , floating and submerged classes...to state that "the removal of larger particles protects one of the key roles of emergent aquatic macrophytes in the wetlands which is the provision
Georgatzis, Konstantinos; Lal, Partha; Hawthorne, Christopher; Shaw, Martin; Piper, Ian; Tarbert, Claire; Donald, Rob; Williams, Christopher K I
2016-01-01
High-resolution, artefact-free and accurately annotated physiological data are desirable in patients with brain injury both to inform clinical decision-making and for intelligent analysis of the data in applications such as predictive modelling. We have quantified the quality of annotation surrounding artefactual events and propose a factorial switching linear dynamical systems (FSLDS) approach to automatically detect artefact in physiological data collected in the neurological intensive care unit (NICU). Retrospective analysis of the BrainIT data set to discover potential hypotensive events corrupted by artefact and identify the annotation of associated clinical interventions. Training of an FSLDS model on clinician-annotated artefactual events in five patients with severe traumatic brain injury. In a subset of 187 patients in the BrainIT database, 26.5 % of potential hypotensive events were abandoned because of artefactual data. Only 30 % of these episodes could be attributed to an annotated clinical intervention. As assessed by the area under the receiver operating characteristic curve metric, FSLDS model performance in automatically identifying the events of blood sampling, arterial line damping and patient handling was 0.978, 0.987 and 0.765, respectively. The influence of artefact on physiological data collected in the NICU is a significant problem. This pilot study using an FSLDS approach shows real promise and is under further development.
NASA Astrophysics Data System (ADS)
Chang, Tsang-Jung; Wang, Chia-Ho; Chen, Albert S.
2015-05-01
In this study, we developed a novel approach to simulate dynamic flow interactions between storm sewers and overland surface for different land covers in urban areas. The proposed approach couples the one-dimensional (1D) sewer flow model (SFM) and the two-dimensional (2D) overland flow model (OFM) with different techniques depending on the land cover type of the study areas. For roads, pavements, plazas, and so forth where rainfall becomes surface runoff before entering the sewer system, the rainfall-runoff process is simulated directly in the 2D OFM, and the runoff is drained to the sewer network via inlets, which is regarded as the input to 1D SFM. For green areas on which rainfall falls into the permeable ground surface and the generated direct runoff traverses terrain, the deduction rate is applied to the rainfall for reflecting the soil infiltration in the 2D OFM. For flat building roofs with drainage facilities allowing rainfall to drain directly from the roof to sewer networks, the rainfall-runoff process is simulated using the hydrological module in the 1D SFM where no rainfall is applied to these areas in the 2D OFM. The 1D SFM is used for hydraulic simulations in the sewer network. Where the flow in the drainage network exceeds its capacity, a surcharge occurs and water may spill onto the ground surface if the pressure head in a manhole exceeds the ground elevation. The overflow discharge from the sewer system is calculated by the 1D SFM and considered a point source in the 2D OFM. The overland flow will return into the sewer network when it reaches an inlet that connects to an un-surcharged manhole. In this case, the inlet is considered as a point sink in the 2D OFM and an inflow to a manhole in the 1D SFM. The proposed approach was compared to other five urban flood modelling techniques with four rainfall events that had previously recorded inundation areas. The merits and drawbacks of each modelling technique were compared and discussed. Based on the
Reaction dynamics in polyatomic molecular systems
Miller, W.H.
1993-12-01
The goal of this program is the development of theoretical methods and models for describing the dynamics of chemical reactions, with specific interest for application to polyatomic molecular systems of special interest and relevance. There is interest in developing the most rigorous possible theoretical approaches and also in more approximate treatments that are more readily applicable to complex systems.
Landscape Construction in Dynamical Systems
NASA Astrophysics Data System (ADS)
Tang, Ying; Yuan, Ruoshi; Wang, Gaowei; Ao, Ping
The idea of landscape has been recently applied to study various of biological problems. We demonstrate that a dynamical structure built into nonlinear dynamical systems allows us to construct such a global optimization landscape, which serves as the Lyapunov function for the ordinary differential equation. We find exact constructions on the landscape for a class of dynamical systems, including a van der Pol type oscillator, competitive Lotka-Volterra systems, and a chaotic system. The landscape constructed provides a new angle for understanding and modelling biological network dynamics.
A neural network approach to dynamic task assignment of multirobots.
Zhu, Anmin; Yang, Simon X
2006-09-01
In this paper, a neural network approach to task assignment, based on a self-organizing map (SOM), is proposed for a multirobot system in dynamic environments subject to uncertainties. It is capable of dynamically controlling a group of mobile robots to achieve multiple tasks at different locations, so that the desired number of robots will arrive at every target location from arbitrary initial locations. In the proposed approach, the robot motion planning is integrated with the task assignment, thus the robots start to move once the overall task is given. The robot navigation can be dynamically adjusted to guarantee that each target location has the desired number of robots, even under uncertainties such as when some robots break down. The proposed approach is capable of dealing with changing environments. The effectiveness and efficiency of the proposed approach are demonstrated by simulation studies.
Overstress and flowstress approaches to dynamic viscoplasticity
NASA Astrophysics Data System (ADS)
Partom, Yehuda
2015-09-01
Viscoplasticity is mostly modelled by the
Leondes, C.T. . Dept. of Electrical Engineering)
1991-01-01
This volume covers topics pertaining to analysis and control system techniques for electric power systems. Topics include: computer relaying in power systems, power system generation expansion, expert systems for power systems, and power flow algorithms.
Dynamical systems, attractors, and neural circuits.
Miller, Paul
2016-01-01
Biology is the study of dynamical systems. Yet most of us working in biology have limited pedagogical training in the theory of dynamical systems, an unfortunate historical fact that can be remedied for future generations of life scientists. In my particular field of systems neuroscience, neural circuits are rife with nonlinearities at all levels of description, rendering simple methodologies and our own intuition unreliable. Therefore, our ideas are likely to be wrong unless informed by good models. These models should be based on the mathematical theories of dynamical systems since functioning neurons are dynamic-they change their membrane potential and firing rates with time. Thus, selecting the appropriate type of dynamical system upon which to base a model is an important first step in the modeling process. This step all too easily goes awry, in part because there are many frameworks to choose from, in part because the sparsely sampled data can be consistent with a variety of dynamical processes, and in part because each modeler has a preferred modeling approach that is difficult to move away from. This brief review summarizes some of the main dynamical paradigms that can arise in neural circuits, with comments on what they can achieve computationally and what signatures might reveal their presence within empirical data. I provide examples of different dynamical systems using simple circuits of two or three cells, emphasizing that any one connectivity pattern is compatible with multiple, diverse functions.
NASA Astrophysics Data System (ADS)
Adamovic, M.; Braud, I.; Branger, F.; Kirchner, J. W.
2014-09-01
This study explores how catchment heterogeneity and variability can be summarized in simplified models, representing the dominant hydrological processes. It focuses on Mediterranean catchments, characterized by heterogeneous geology, pedology, and land use, as well as steep topography and a rainfall regime in which summer droughts contrast with high-rainfall periods in autumn. The Ardèche catchment (south-east France), typical of this environment, is chosen to explore the following questions: (1) can such a Mediterranean catchment be adequately characterized by simple dynamical systems approach and what are the limits of the method under such conditions? (2) What information about dominant predictors of hydrological variability can be retrieved from this analysis in such catchments? In this work we apply the data-driven approach of Kirchner (WRR, 2009) to estimate discharge sensitivity functions that summarize the behavior of four sub-catchments of the Ardèche, using non-vegetation periods (November-March) from 9 years of data (2000-2008) from operational networks. The relevance of the inferred sensitivity function is assessed through hydrograph simulations, and through estimating precipitation rates from discharge fluctuations. We find that the discharge-sensitivity function is downward-curving in double-logarithmic space, thus allowing further simulation of discharge and non-divergence of the model, only during non-vegetation periods. The analysis is complemented by a Monte-Carlo sensitivity analysis showing how the parameters summarizing the discharge sensitivity function impact the simulated hydrographs. The resulting discharge simulation results are good for granite catchments, found to be predominantly characterized by saturation excess runoff and sub-surface flow processes. The simple dynamical system hypothesis works especially well in wet conditions (peaks and recessions are well modeled). On the other hand, poor model performance is associated with
Dynamical systems theory for music dynamics.
Boon, Jean Pierre; Decroly, Olivier
1995-09-01
We show that, when music pieces are cast in the form of time series of pitch variations, the concepts and tools of dynamical systems theory can be applied to the analysis of temporal dynamics in music. (i) Phase space portraits are constructed from the time series wherefrom the dimensionality is evaluated as a measure of the global dynamics of each piece. (ii) Spectral analysis of the time series yields power spectra ( approximately f(-nu)) close to red noise (nu approximately 2) in the low frequency range. (iii) We define an information entropy which provides a measure of the local dynamics in the musical piece; the entropy can be interpreted as an evaluation of the degree of complexity in the music, but there is no evidence of an analytical relation between local and global dynamics. These findings are based on computations performed on eighty sequences sampled in the music literature from the 18th to the 20th century. (c) 1995 American Institute of Physics.
The effective field theorist's approach to gravitational dynamics
NASA Astrophysics Data System (ADS)
Porto, Rafael A.
2016-05-01
We review the effective field theory (EFT) approach to gravitational dynamics. We focus on extended objects in long-wavelength backgrounds and gravitational wave emission from spinning binary systems. We conclude with an introduction to EFT methods for the study of cosmological large scale structures.
Stock market networks: The dynamic conditional correlation approach
NASA Astrophysics Data System (ADS)
Lyócsa, Štefan; Výrost, Tomáš; Baumöhl, Eduard
2012-08-01
We demonstrate the economic relevance of minimum spanning trees (MSTs) constructed from dynamic conditional correlations (DCC) for a sample of S&P 100 constituents. An empirical comparison of MST properties shows that using the standard approach of rolling (or sliding-window) correlations yields trees that are more robust, have higher densities and exhibit higher industry clustering than MSTs based on DCC. Our results suggest that these properties are achieved at the expense of the smoothing of market dynamics, which is better preserved by DCC. The DCC approach offers a new perspective for the analysis of complex systems such as stock markets.
Nonlinear systems approach to control system design
NASA Technical Reports Server (NTRS)
Meyer, G.
1984-01-01
Consider some of the control system design methods for plants with nonlinear dynamics. If the nonlinearity is weak relative to the size of the operating region, then the linear methods apply directly. Fixed-gain design may be feasible even for significant nonlinearities. It may be possible to find a single gain which provides adequate control of the linear models at several perturbation points. If the nonlinearity is restricted to a sector, that fact may be used to obtain a fixed-gain controller. Otherwise, a gain may have to be associated with each perturbation point Pi. A gain schedule K(p(v)) is obtained by connecting the perturbation points by a function, say p(v), of the scheduling parameter v (i.e., speed). When the scheduling parameter must be multidimensional, this approach is difficult; the objective is to develop an easier procedure.
NASA Astrophysics Data System (ADS)
Parsons, Todd L.; Rogers, Tim
2017-10-01
Systems composed of large numbers of interacting agents often admit an effective coarse-grained description in terms of a multidimensional stochastic dynamical system, driven by small-amplitude intrinsic noise. In applications to biological, ecological, chemical and social dynamics it is common for these models to posses quantities that are approximately conserved on short timescales, in which case system trajectories are observed to remain close to some lower-dimensional subspace. Here, we derive explicit and general formulae for a reduced-dimension description of such processes that is exact in the limit of small noise and well-separated slow and fast dynamics. The Michaelis–Menten law of enzyme-catalysed reactions, and the link between the Lotka–Volterra and Wright–Fisher processes are explored as a simple worked examples. Extensions of the method are presented for infinite dimensional systems and processes coupled to non-Gaussian noise sources.
NASA Astrophysics Data System (ADS)
Shabani, Hamid; Ziaie, Amir Hadi
2017-05-01
Very recently, Josset and Perez (Phys. Rev. Lett. 118:021102, 2017) have shown that a violation of the energy-momentum tensor ( EMT) could result in an accelerated expansion state via the appearance of an effective cosmological constant, in the context of unimodular gravity. Inspired by this outcome, in this paper we investigate cosmological consequences of a violation of the EMT conservation in a particular class of f(R,T) gravity when only the pressure-less fluid is present. In this respect, we focus on the late time solutions of models of the type f(R,T)=R+β Λ (-T). As the first task, we study the solutions when the conservation of EMT is respected, and then we proceed with those in which violation occurs. We have found, provided that the EMT conservation is violated, that there generally exist two accelerated expansion solutions of which the stability properties depend on the underlying model. More exactly, we obtain a dark energy solution for which the effective equation of state depends on the model parameters and a de Sitter solution. We present a method to parametrize the Λ (-T) function, which is useful in a dynamical system approach and has been employed in the model. Also, we discuss the cosmological solutions for models with Λ (-T)=8π G(-T)^{α } in the presence of ultra-relativistic matter.
NASA Astrophysics Data System (ADS)
Mohammadi Nasrabadi, Ali; Hosseinpour, Mohammad Hossein; Ebrahimnejad, Sadoullah
2013-05-01
In competitive markets, market segmentation is a critical point of business, and it can be used as a generic strategy. In each segment, strategies lead companies to their targets; thus, segment selection and the application of the appropriate strategies over time are very important to achieve successful business. This paper aims to model a strategy-aligned fuzzy approach to market segment evaluation and selection. A modular decision support system (DSS) is developed to select an optimum segment with its appropriate strategies. The suggested DSS has two main modules. The first one is SPACE matrix which indicates the risk of each segment. Also, it determines the long-term strategies. The second module finds the most preferred segment-strategies over time. Dynamic network process is applied to prioritize segment-strategies according to five competitive force factors. There is vagueness in pairwise comparisons, and this vagueness has been modeled using fuzzy concepts. To clarify, an example is illustrated by a case study in Iran's coffee market. The results show that success possibility of segments could be different, and choosing the best ones could help companies to be sure in developing their business. Moreover, changing the priority of strategies over time indicates the importance of long-term planning. This fact has been supported by a case study on strategic priority difference in short- and long-term consideration.
An analytic approach to cyber adversarial dynamics
NASA Astrophysics Data System (ADS)
Sweeney, Patrick; Cybenko, George
2012-06-01
To date, cyber security investment by both the government and commercial sectors has been largely driven by the myopic best response of players to the actions of their adversaries and their perception of the adversarial environment. However, current work in applying traditional game theory to cyber operations typically assumes that games exist with prescribed moves, strategies, and payos. This paper presents an analytic approach to characterizing the more realistic cyber adversarial metagame that we believe is being played. Examples show that understanding the dynamic metagame provides opportunities to exploit an adversary's anticipated attack strategy. A dynamic version of a graph-based attack-defend game is introduced, and a simulation shows how an optimal strategy can be selected for success in the dynamic environment.
Generating Dynamic System Matrices for Dynamic SPECT
2011-02-01
The purpose of the computer program is to generate system matrices that model data acquisition process in dynamic single photon emission computed tomography (SPECT). The application is for the reconstruction of dynamic data from projection measurements that provide the time evolution of activity uptake and wash out in an organ of interest. The measurement of the time activity in the blood and organ tissue provide time-activity curves (TACs) that are used to estimate kinetic parameters. The program provides a correct model of the in vivo spatial and temporal distribution of radioactive in organs. The model accounts for the attenuation of the internal emitting radioactivity, it accounts for the vary point response of the collimators, and correctly models the time variation of the activity in the organs. One important application where the software is being used in a measuring the arterial input function (AIF) in a dynamic SPECT study where the data are acquired from a slow camera rotation. Measurement of the arterial input function (AIF) is essential to deriving quantitative estimates of regional myocardial blood flow using kinetic models. A study was performed to evaluate whether a slowly rotating SPECT system could provide accurate AIF's for myocardial perfusion imaging (MPI). Methods: Dynamic cardiac SPECT was first performed in human subjects at rest using a Phillips Precedence SPECT/CT scanner. Dynamic measurements of Tc-99m-tetrofosmin in the myocardium were obtained using an infusion time of 2 minutes. Blood input, myocardium tissue and liver TACs were estimated using spatiotemporal splines. These were fit to a one-compartment perfusion model to obtain wash-in rate parameters K1. Results: The spatiotemporal 4D ML-EM reconstructions gave more accurate reconstructions that did standard frame-by-frame 3D ML-EM reconstructions. From additional computer simulations and phantom studies, it was determined that a 1 minute infusion with a SPECT system rotation speed
Dynamical systems, attractors, and neural circuits
Miller, Paul
2016-01-01
Biology is the study of dynamical systems. Yet most of us working in biology have limited pedagogical training in the theory of dynamical systems, an unfortunate historical fact that can be remedied for future generations of life scientists. In my particular field of systems neuroscience, neural circuits are rife with nonlinearities at all levels of description, rendering simple methodologies and our own intuition unreliable. Therefore, our ideas are likely to be wrong unless informed by good models. These models should be based on the mathematical theories of dynamical systems since functioning neurons are dynamic—they change their membrane potential and firing rates with time. Thus, selecting the appropriate type of dynamical system upon which to base a model is an important first step in the modeling process. This step all too easily goes awry, in part because there are many frameworks to choose from, in part because the sparsely sampled data can be consistent with a variety of dynamical processes, and in part because each modeler has a preferred modeling approach that is difficult to move away from. This brief review summarizes some of the main dynamical paradigms that can arise in neural circuits, with comments on what they can achieve computationally and what signatures might reveal their presence within empirical data. I provide examples of different dynamical systems using simple circuits of two or three cells, emphasizing that any one connectivity pattern is compatible with multiple, diverse functions. PMID:27408709
Leondes, C.T. . Dept. of Electrical Engineering)
1991-01-01
This book covers analysis and control system techniques for electric power systems. Topics include: concurrent processing in power system analysis, power system protection, voltage collapse, reliability techniques in large electric power systems, optimization in hydroelectric systems, and linear programming methods for optimal energy plant operation.
Physical approaches to the dynamics of genetic circuits: a tutorial
NASA Astrophysics Data System (ADS)
Garcia-Ojalvo, Jordi
2011-09-01
Cellular behaviour is governed by gene regulatory processes that are intrinsically dynamic and nonlinear, and are subject to non-negligible amounts of random fluctuations. Such conditions are ubiquitous in physical systems, where they have been studied for decades using the tools of statistical and nonlinear physics. The goal of this introductory tutorial is to show how approaches traditionally used in physics can help in reaching a systems-level understanding of living cells. To that end, we present an overview of the dynamical phenomena exhibited by genetic circuits and their functional significance. We also describe the theoretical and experimental approaches that are being used to unravel the relationship between circuit structure and function in dynamical cellular processes under the influence ofnoise. Studies are discussed both at the single-cell level and in cellular populations, where intercellular coupling plays an important role.
Nonlinear dynamic macromodeling techniques for audio systems
NASA Astrophysics Data System (ADS)
Ogrodzki, Jan; Bieńkowski, Piotr
2015-09-01
This paper develops a modelling method and a models identification technique for the nonlinear dynamic audio systems. Identification is performed by means of a behavioral approach based on a polynomial approximation. This approach makes use of Discrete Fourier Transform and Harmonic Balance Method. A model of an audio system is first created and identified and then it is simulated in real time using an algorithm of low computational complexity. The algorithm consists in real time emulation of the system response rather than in simulation of the system itself. The proposed software is written in Python language using object oriented programming techniques. The code is optimized for a multithreads environment.
A residual flexibility approach to multibody dynamics
NASA Technical Reports Server (NTRS)
Blelloch, Paul A.; Antal, Gregory W.
1993-01-01
Many complex systems can be modeled as a collection of interacting bodies, where the relative motion of the bodies may be large. The dynamics of such systems are simulated using multibody dynamic formulations. Many of these treat each body as a rigid component, but recently the flexibility of the components has been incorporated. This paper presents a residual flexibility formulation of the multibody dynamics problem. The formulation is very simple and offers great computational efficiency since it treats each body as a free structure in space, interacting with other bodies only through interface forces. Each body's accelerations can be solved independently, as can each set of interface forces. We have applied the technique successfully to several special applications, and the initial implementation in a general mechanisms code has given excellent results in comparison to a direct finite element representation of flexibility.
Solar dynamic space power system heat rejection
NASA Technical Reports Server (NTRS)
Carlson, A. W.; Gustafson, E.; Mclallin, K. L.
1986-01-01
A radiator system concept is described that meets the heat rejection requirements of the NASA Space Station solar dynamic power modules. The heat pipe radiator is a high-reliability, high-performance approach that is capable of erection in space and is maintainable on orbit. Results are present of trade studies that compare the radiator system area and weight estimates for candidate advanced high performance heat pipes. The results indicate the advantages of the dual-slot heat pipe radiator for high temperature applications as well as its weight-reduction potential over the range of temperatures to be encountered in the solar dynamic heat rejection systems.
Detecting Recurrence Domains of Dynamical Systems by Symbolic Dynamics
NASA Astrophysics Data System (ADS)
Graben, Peter beim; Hutt, Axel
2013-04-01
We propose an algorithm for the detection of recurrence domains of complex dynamical systems from time series. Our approach exploits the characteristic checkerboard texture of recurrence domains exhibited in recurrence plots. In phase space, recurrence plots yield intersecting balls around sampling points that could be merged into cells of a phase space partition. We construct this partition by a rewriting grammar applied to the symbolic dynamics of time indices. A maximum entropy principle defines the optimal size of intersecting balls. The final application to high-dimensional brain signals yields an optimal symbolic recurrence plot revealing functional components of the signal.
Understanding and Modeling Teams As Dynamical Systems
Gorman, Jamie C.; Dunbar, Terri A.; Grimm, David; Gipson, Christina L.
2017-01-01
By its very nature, much of teamwork is distributed across, and not stored within, interdependent people working toward a common goal. In this light, we advocate a systems perspective on teamwork that is based on general coordination principles that are not limited to cognitive, motor, and physiological levels of explanation within the individual. In this article, we present a framework for understanding and modeling teams as dynamical systems and review our empirical findings on teams as dynamical systems. We proceed by (a) considering the question of why study teams as dynamical systems, (b) considering the meaning of dynamical systems concepts (attractors; perturbation; synchronization; fractals) in the context of teams, (c) describe empirical studies of team coordination dynamics at the perceptual-motor, cognitive-behavioral, and cognitive-neurophysiological levels of analysis, and (d) consider the theoretical and practical implications of this approach, including new kinds of explanations of human performance and real-time analysis and performance modeling. Throughout our discussion of the topics we consider how to describe teamwork using equations and/or modeling techniques that describe the dynamics. Finally, we consider what dynamical equations and models do and do not tell us about human performance in teams and suggest future research directions in this area. PMID:28744231
A System Dynamic Model of Leader Emergence
2008-03-01
complexity and organizational sciences. Applying complexity science to leadership research expands previous notions of leadership beyond dyadic...Contingency approaches to leadership suggest that environmental conditions combined with leader behavoirs , determine leader effectiveness (Judge...events and represents the foundation of understanding system dynamics. Feedback in organizational behavior parlance is simply the reaction to a
Dynamical approach to the Casimir effect.
Rodriguez-Lopez, P; Brito, R; Soto, R
2011-03-01
Casimir forces can appear between intrusions placed in different media driven by several fluctuation mechanisms, either in equilibrium or out of it. Herein, we develop a general formalism to obtain such forces from the dynamical equations of the fluctuating medium, the statistical properties of the driving noise, and the boundary conditions of the intrusions (which simulate the interaction between the intrusions and the medium). As a result, an explicit formula for the Casimir force over the intrusions is derived. This formalism contains the thermal Casimir effect as a particular limit and generalizes the study of the Casimir effect to such systems through their dynamical equations, with no appeal to their Hamiltonian, if any exists. In particular, we study the Casimir force between two infinite parallel plates with Dirichlet or Neumann boundary conditions, immersed in several media with finite correlation lengths (reaction-diffusion system, liquid crystals, and two coupled fields with non-Hermitian evolution equations). The driving Gaussian noises have vanishing or finite spatial or temporal correlation lengths; in the first case, equilibrium is reobtained and finite correlations produce nonequilibrium dynamics. The results obtained show that, generally, nonequilibrium dynamics leads to Casimir forces, whereas Casimir forces are obtained in equilibrium dynamics if the stress tensor is anisotropic.
da Silva, Roberto; Drugowich de Felício, José Roberto; Martinez, Alexandre Souto
2012-06-01
The extension of Boltzmann-Gibbs thermostatistics, proposed by Tsallis, introduces an additional parameter q to the inverse temperature β. Here, we show that a previously introduced generalized Metropolis dynamics to evolve spin models is not local and does not obey the detailed energy balance. In this dynamics, locality is only retrieved for q=1, which corresponds to the standard Metropolis algorithm. Nonlocality implies very time-consuming computer calculations, since the energy of the whole system must be reevaluated when a single spin is flipped. To circumvent this costly calculation, we propose a generalized master equation, which gives rise to a local generalized Metropolis dynamics that obeys the detailed energy balance. To compare the different critical values obtained with other generalized dynamics, we perform Monte Carlo simulations in equilibrium for the Ising model. By using short-time nonequilibrium numerical simulations, we also calculate for this model the critical temperature and the static and dynamical critical exponents as functions of q. Even for q≠1, we show that suitable time-evolving power laws can be found for each initial condition. Our numerical experiments corroborate the literature results when we use nonlocal dynamics, showing that short-time parameter determination works also in this case. However, the dynamics governed by the new master equation leads to different results for critical temperatures and also the critical exponents affecting universality classes. We further propose a simple algorithm to optimize modeling the time evolution with a power law, considering in a log-log plot two successive refinements.
Hamiltonian Approach to the Dynamical Casimir Effect
Haro, Jaume; Elizalde, Emilio
2006-09-29
A Hamiltonian approach is introduced in order to address some severe problems associated with the physical description of the dynamical Casimir effect at all times. For simplicity, the case of a neutral scalar field in a one-dimensional cavity with partially transmitting mirrors (an essential proviso) is considered, but the method can be extended to fields of any kind and higher dimensions. The motional force calculated in our approach contains a reactive term--proportional to the mirrors' acceleration - which is fundamental in order to obtain (quasi)particles with a positive energy all the time during the movement of the mirrors - while always satisfying the energy conservation law. Comparisons with other approaches and a careful analysis of the interrelations among the different results previously obtained in the literature are carried out.
Understanding Digital Learning from the Perspective of Systems Dynamics
ERIC Educational Resources Information Center
Kok, Ayse
2009-01-01
The System Dynamics approach can be seen as a new way of understanding dynamical phenonema (natural, physical, biological, etc.) that occur in our daily lives taking into consideration not only single pairs of cause-effect variables, but the functioning of the system as a whole. This approach also provides the students with a new understanding in…
Ergatic dynamic control systems
NASA Technical Reports Server (NTRS)
Pavlov, V. V. (Editor); Drozdova, T. I. (Editor); Antomonov, Y. G. (Editor); Golego, V. N. (Editor); Ivakhnenko, A. G. (Editor); Meleshev, A. M. (Editor)
1977-01-01
Synthesis and analysis of systems containing a man in their control circuits are considered. The concepts of ergonomics and ergatic systems are defined, and tasks and problems of ergonomics are outlined. The synthesis of the structure of an astronautic ergatic organism is presented, as well as the synthesis of nonstationary ergatic systems. Problems of selecting the criteria for complex systems are considered, and the results are presented from a study of ergatic control systems with any degree of human participation.
Nonlinear dynamic analysis of flexible multibody systems
NASA Technical Reports Server (NTRS)
Bauchau, Olivier A.; Kang, Nam Kook
1991-01-01
Two approaches are developed to analyze the dynamic behavior of flexible multibody systems. In the first approach each body is modeled with a modal methodology in a local non-inertial frame of reference, whereas in the second approach, each body is modeled with a finite element methodology in the inertial frame. In both cases, the interaction among the various elastic bodies is represented by constraint equations. The two approaches were compared for accuracy and efficiency: the first approach is preferable when the nonlinearities are not too strong but it becomes cumbersome and expensive to use when many modes must be used. The second approach is more general and easier to implement but could result in high computation costs for a large system. The constraints should be enforced in a time derivative fashion for better accuracy and stability.
Reduced dynamics with initial correlations: Multiconfigurational approach
NASA Astrophysics Data System (ADS)
Burghardt, I.
2001-01-01
Dynamical equations for a subsystem interacting with an environment are proposed which are adapted to a multiconfigurational form of the density operator. Initial correlations are accounted for in a non-Markovian master equation. Two variants of the latter are derived by projection operator techniques and cumulant expansion techniques, respectively. The present scheme is developed in view of describing the ultrafast dynamics in solute-solvent complexes where the details of system-environment correlations are of importance. The master equation is readily integrated into the equations of motion derived by the multiconfiguration time-dependent Hartree method, which provides an efficient scheme for the numerical propagation of the density operator.
Advances in Quantum Trajectory Approaches to Dynamics
NASA Astrophysics Data System (ADS)
Askar, Attila
2001-03-01
The quantum fluid dynamics (QFD) formulation is based on the separation of the amplitude and phase of the complex wave function in Schrodinger's equation. The approach leads to conservation laws for an equivalent "gas continuum". The Lagrangian [1] representation corresponds to following the particles of the fluid continuum, i. e. calculating "quantum trajectories". The Eulerian [2] representation on the other hand, amounts to observing the dynamics of the gas continuum at the points of a fixed coordinate frame. The combination of several factors leads to a most encouraging computational efficiency. QFD enables the numerical analysis to deal with near monotonic amplitude and phase functions. The Lagrangian description concentrates the computation effort to regions of highest probability as an optimal adaptive grid. The Eulerian representation allows the study of multi-coordinate problems as a set of one-dimensional problems within an alternating direction methodology. An explicit time integrator limits the increase in computational effort with the number of discrete points to linear. Discretization of the space via local finite elements [1,2] and global radial functions [3] will be discussed. Applications include wave packets in four-dimensional quadratic potentials and two coordinate photo-dissociation problems for NOCl and NO2. [1] "Quantum fluid dynamics (QFD) in the Lagrangian representation with applications to photo-dissociation problems", F. Sales, A. Askar and H. A. Rabitz, J. Chem. Phys. 11, 2423 (1999) [2] "Multidimensional wave-packet dynamics within the fluid dynamical formulation of the Schrodinger equation", B. Dey, A. Askar and H. A. Rabitz, J. Chem. Phys. 109, 8770 (1998) [3] "Solution of the quantum fluid dynamics equations with radial basis function interpolation", Xu-Guang Hu, Tak-San Ho, H. A. Rabitz and A. Askar, Phys. Rev. E. 61, 5967 (2000)
Dynamics robustness of cascading systems.
Young, Jonathan T; Hatakeyama, Tetsuhiro S; Kaneko, Kunihiko
2017-03-01
A most important property of biochemical systems is robustness. Static robustness, e.g., homeostasis, is the insensitivity of a state against perturbations, whereas dynamics robustness, e.g., homeorhesis, is the insensitivity of a dynamic process. In contrast to the extensively studied static robustness, dynamics robustness, i.e., how a system creates an invariant temporal profile against perturbations, is little explored despite transient dynamics being crucial for cellular fates and are reported to be robust experimentally. For example, the duration of a stimulus elicits different phenotypic responses, and signaling networks process and encode temporal information. Hence, robustness in time courses will be necessary for functional biochemical networks. Based on dynamical systems theory, we uncovered a general mechanism to achieve dynamics robustness. Using a three-stage linear signaling cascade as an example, we found that the temporal profiles and response duration post-stimulus is robust to perturbations against certain parameters. Then analyzing the linearized model, we elucidated the criteria of when signaling cascades will display dynamics robustness. We found that changes in the upstream modules are masked in the cascade, and that the response duration is mainly controlled by the rate-limiting module and organization of the cascade's kinetics. Specifically, we found two necessary conditions for dynamics robustness in signaling cascades: 1) Constraint on the rate-limiting process: The phosphatase activity in the perturbed module is not the slowest. 2) Constraints on the initial conditions: The kinase activity needs to be fast enough such that each module is saturated even with fast phosphatase activity and upstream changes are attenuated. We discussed the relevance of such robustness to several biological examples and the validity of the above conditions therein. Given the applicability of dynamics robustness to a variety of systems, it will provide a
Dynamics robustness of cascading systems
Kaneko, Kunihiko
2017-01-01
A most important property of biochemical systems is robustness. Static robustness, e.g., homeostasis, is the insensitivity of a state against perturbations, whereas dynamics robustness, e.g., homeorhesis, is the insensitivity of a dynamic process. In contrast to the extensively studied static robustness, dynamics robustness, i.e., how a system creates an invariant temporal profile against perturbations, is little explored despite transient dynamics being crucial for cellular fates and are reported to be robust experimentally. For example, the duration of a stimulus elicits different phenotypic responses, and signaling networks process and encode temporal information. Hence, robustness in time courses will be necessary for functional biochemical networks. Based on dynamical systems theory, we uncovered a general mechanism to achieve dynamics robustness. Using a three-stage linear signaling cascade as an example, we found that the temporal profiles and response duration post-stimulus is robust to perturbations against certain parameters. Then analyzing the linearized model, we elucidated the criteria of when signaling cascades will display dynamics robustness. We found that changes in the upstream modules are masked in the cascade, and that the response duration is mainly controlled by the rate-limiting module and organization of the cascade’s kinetics. Specifically, we found two necessary conditions for dynamics robustness in signaling cascades: 1) Constraint on the rate-limiting process: The phosphatase activity in the perturbed module is not the slowest. 2) Constraints on the initial conditions: The kinase activity needs to be fast enough such that each module is saturated even with fast phosphatase activity and upstream changes are attenuated. We discussed the relevance of such robustness to several biological examples and the validity of the above conditions therein. Given the applicability of dynamics robustness to a variety of systems, it will provide a
Operationalizing sustainability in urban coastal systems: a system dynamics analysis.
Mavrommati, Georgia; Bithas, Kostas; Panayiotidis, Panayiotis
2013-12-15
We propose a system dynamics approach for Ecologically Sustainable Development (ESD) in urban coastal systems. A systematic analysis based on theoretical considerations, policy analysis and experts' knowledge is followed in order to define the concept of ESD. The principles underlying ESD feed the development of a System Dynamics Model (SDM) that connects the pollutant loads produced by urban systems' socioeconomic activities with the ecological condition of the coastal ecosystem that it is delineated in operational terms through key biological elements defined by the EU Water Framework Directive. The receiving waters of the Athens Metropolitan area, which bears the elements of typical high population density Mediterranean coastal city but which currently has also new dynamics induced by the ongoing financial crisis, are used as an experimental system for testing a system dynamics approach to apply the concept of ESD. Systems' thinking is employed to represent the complex relationships among the components of the system. Interconnections and dependencies that determine the potentials for achieving ESD are revealed. The proposed system dynamics analysis can facilitate decision makers to define paths of development that comply with the principles of ESD. Copyright © 2013 Elsevier Ltd. All rights reserved.
Dynamic granularity of imaging systems
Geissel, Matthias; Smith, Ian C.; Shores, Jonathon E.; Porter, John L.
2015-11-04
Imaging systems that include a specific source, imaging concept, geometry, and detector have unique properties such as signal-to-noise ratio, dynamic range, spatial resolution, distortions, and contrast. Some of these properties are inherently connected, particularly dynamic range and spatial resolution. It must be emphasized that spatial resolution is not a single number but must be seen in the context of dynamic range and consequently is better described by a function or distribution. We introduce the “dynamic granularity” G_{dyn} as a standardized, objective relation between a detector’s spatial resolution (granularity) and dynamic range for complex imaging systems in a given environment rather than the widely found characterization of detectors such as cameras or films by themselves. We found that this relation can partly be explained through consideration of the signal’s photon statistics, background noise, and detector sensitivity, but a comprehensive description including some unpredictable data such as dust, damages, or an unknown spectral distribution will ultimately have to be based on measurements. Measured dynamic granularities can be objectively used to assess the limits of an imaging system’s performance including all contributing noise sources and to qualify the influence of alternative components within an imaging system. Our article explains the construction criteria to formulate a dynamic granularity and compares measured dynamic granularities for different detectors used in the X-ray backlighting scheme employed at Sandia’s Z-Backlighter facility.
Dynamic granularity of imaging systems
Geissel, Matthias; Smith, Ian C.; Shores, Jonathon E.; ...
2015-11-04
Imaging systems that include a specific source, imaging concept, geometry, and detector have unique properties such as signal-to-noise ratio, dynamic range, spatial resolution, distortions, and contrast. Some of these properties are inherently connected, particularly dynamic range and spatial resolution. It must be emphasized that spatial resolution is not a single number but must be seen in the context of dynamic range and consequently is better described by a function or distribution. We introduce the “dynamic granularity” Gdyn as a standardized, objective relation between a detector’s spatial resolution (granularity) and dynamic range for complex imaging systems in a given environment rathermore » than the widely found characterization of detectors such as cameras or films by themselves. We found that this relation can partly be explained through consideration of the signal’s photon statistics, background noise, and detector sensitivity, but a comprehensive description including some unpredictable data such as dust, damages, or an unknown spectral distribution will ultimately have to be based on measurements. Measured dynamic granularities can be objectively used to assess the limits of an imaging system’s performance including all contributing noise sources and to qualify the influence of alternative components within an imaging system. Our article explains the construction criteria to formulate a dynamic granularity and compares measured dynamic granularities for different detectors used in the X-ray backlighting scheme employed at Sandia’s Z-Backlighter facility.« less
Traditional Chinese medicine: potential approaches from modern dynamical complexity theories.
Ma, Yan; Zhou, Kehua; Fan, Jing; Sun, Shuchen
2016-03-01
Despite the widespread use of traditional Chinese medicine (TCM) in clinical settings, proving its effectiveness via scientific trials is still a challenge. TCM views the human body as a complex dynamical system, and focuses on the balance of the human body, both internally and with its external environment. Such fundamental concepts require investigations using system-level quantification approaches, which are beyond conventional reductionism. Only methods that quantify dynamical complexity can bring new insights into the evaluation of TCM. In a previous article, we briefly introduced the potential value of Multiscale Entropy (MSE) analysis in TCM. This article aims to explain the existing challenges in TCM quantification, to introduce the consistency of dynamical complexity theories and TCM theories, and to inspire future system-level research on health and disease.
Bouzguenda, Lotfi; Turki, Manel
2014-04-01
This paper shows how the combined use of agent and web services technologies can help to design an architectural style for dynamic medical Cross-Organizational Workflow (COW) management system. Medical COW aims at supporting the collaboration between several autonomous and possibly heterogeneous medical processes, distributed over different organizations (Hospitals, Clinic or laboratories). Dynamic medical COW refers to occasional cooperation between these health organizations, free of structural constraints, where the medical partners involved and their number are not pre-defined. More precisely, this paper proposes a new architecture style based on agents and web services technologies to deal with two key coordination issues of dynamic COW: medical partners finding and negotiation between them. It also proposes how the proposed architecture for dynamic medical COW management system can connect to a multi-agent system coupling the Clinical Decision Support System (CDSS) with Computerized Prescriber Order Entry (CPOE). The idea is to assist the health professionals such as doctors, nurses and pharmacists with decision making tasks, as determining diagnosis or patient data analysis without stopping their clinical processes in order to act in a coherent way and to give care to the patient.
Gauge-invariant approach to quark dynamics
NASA Astrophysics Data System (ADS)
Sazdjian, H.
2016-02-01
The main aspects of a gauge-invariant approach to the description of quark dynamics in the nonperturbative regime of quantum chromodynamics (QCD) are first reviewed. The role of the parallel transport operation in constructing gauge-invariant Green's functions is then presented, and the relevance of Wilson loops for the representation of the interaction is emphasized. Recent developments, based on the use of polygonal lines for the parallel transport operation, are presented. An integro-differential equation, obtained for the quark Green's function defined with a phase factor along a single, straight line segment, is solved exactly and analytically in the case of two-dimensional QCD in the large- N c limit. The solution displays the dynamical mass generation phenomenon for quarks, with an infinite number of branch-cut singularities that are stronger than simple poles.
Nogueiras, Gloria; Kunnen, E. Saskia; Iborra, Alejandro
2017-01-01
This study adopts a dynamic systems approach to investigate how individuals successfully manage contextual complexity. To that end, we tracked individuals' emotional trajectories during a challenging training course, seeking qualitative changes–turning points—and we tested their relationship with the perceived complexity of the training. The research context was a 5-day higher education course based on process-oriented experiential learning, and the sample consisted of 17 students. The students used a five-point Likert scale to rate the intensity of 16 emotions and the complexity of the training on 8 measurement points. Monte Carlo permutation tests enabled to identify 30 turning points in the 272 emotional trajectories analyzed (17 students * 16 emotions each). 83% of the turning points indicated a change of pattern in the emotional trajectories that consisted of: (a) increasingly intense positive emotions or (b) decreasingly intense negative emotions. These turning points also coincided with particularly complex periods in the training as perceived by the participants (p = 0.003, and p = 0.001 respectively). The relationship between positively-trended turning points in the students' emotional trajectories and the complexity of the training may be interpreted as evidence of a successful management of the cognitive conflict arising from the clash between the students' prior ways of meaning-making and the challenging demands of the training. One of the strengths of this study is that it provides a relatively simple procedure for identifying turning points in developmental trajectories, which can be applied to various longitudinal experiences that are very common in educational and developmental contexts. Additionally, the findings contribute to sustaining that the assumption that complex contextual demands lead unfailingly to individuals' learning is incomplete. Instead, it is how individuals manage complexity which may or may not lead to learning. Finally, this
Nogueiras, Gloria; Kunnen, E Saskia; Iborra, Alejandro
2017-01-01
This study adopts a dynamic systems approach to investigate how individuals successfully manage contextual complexity. To that end, we tracked individuals' emotional trajectories during a challenging training course, seeking qualitative changes-turning points-and we tested their relationship with the perceived complexity of the training. The research context was a 5-day higher education course based on process-oriented experiential learning, and the sample consisted of 17 students. The students used a five-point Likert scale to rate the intensity of 16 emotions and the complexity of the training on 8 measurement points. Monte Carlo permutation tests enabled to identify 30 turning points in the 272 emotional trajectories analyzed (17 students (*) 16 emotions each). 83% of the turning points indicated a change of pattern in the emotional trajectories that consisted of: (a) increasingly intense positive emotions or (b) decreasingly intense negative emotions. These turning points also coincided with particularly complex periods in the training as perceived by the participants (p = 0.003, and p = 0.001 respectively). The relationship between positively-trended turning points in the students' emotional trajectories and the complexity of the training may be interpreted as evidence of a successful management of the cognitive conflict arising from the clash between the students' prior ways of meaning-making and the challenging demands of the training. One of the strengths of this study is that it provides a relatively simple procedure for identifying turning points in developmental trajectories, which can be applied to various longitudinal experiences that are very common in educational and developmental contexts. Additionally, the findings contribute to sustaining that the assumption that complex contextual demands lead unfailingly to individuals' learning is incomplete. Instead, it is how individuals manage complexity which may or may not lead to learning. Finally, this
Dynamical Systems and Oceanography
1994-04-25
8217SECURITY CLASSIFICATION OF THIS PAGE 7 JREOC1AD-A282 635APIr---- 1 Form Ap! ve Ia. REPORT SECURITY ELSIFC AD A 8 635 . 0 of 2SECURITY CLASSIFICATION...mathematical approach should prove ideal for analyzing transport and mixing processes associated with the large scale , organized motions observed in
Bhatt, Uma S.; Wackerbauer, Renate; Polyakov, Igor V.; Newman, David E.; Sanchez, Raul E.
2015-11-13
The goal of this research was to apply fractional and non-linear analysis techniques in order to develop a more complete characterization of climate change and variability for the oceanic, sea ice and atmospheric components of the Earth System. This research applied two measures of dynamical characteristics of time series, the R/S method of calculating the Hurst exponent and Renyi entropy, to observational and modeled climate data in order to evaluate how well climate models capture the long-term dynamics evident in observations. Fractional diffusion analysis was applied to ARGO ocean buoy data to quantify ocean transport. Self organized maps were applied to North Pacific sea level pressure and analyzed in ways to improve seasonal predictability for Alaska fire weather. This body of research shows that these methods can be used to evaluate climate models and shed light on climate mechanisms (i.e., understanding why something happens). With further research, these methods show promise for improving seasonal to longer time scale forecasts of climate.
Dynamical Signatures of Living Systems
NASA Technical Reports Server (NTRS)
Zak, M.
1999-01-01
One of the main challenges in modeling living systems is to distinguish a random walk of physical origin (for instance, Brownian motions) from those of biological origin and that will constitute the starting point of the proposed approach. As conjectured, the biological random walk must be nonlinear. Indeed, any stochastic Markov process can be described by linear Fokker-Planck equation (or its discretized version), only that type of process has been observed in the inanimate world. However, all such processes always converge to a stable (ergodic or periodic) state, i.e., to the states of a lower complexity and high entropy. At the same time, the evolution of living systems directed toward a higher level of complexity if complexity is associated with a number of structural variations. The simplest way to mimic such a tendency is to incorporate a nonlinearity into the random walk; then the probability evolution will attain the features of diffusion equation: the formation and dissipation of shock waves initiated by small shallow wave disturbances. As a result, the evolution never "dies:" it produces new different configurations which are accompanied by an increase or decrease of entropy (the decrease takes place during formation of shock waves, the increase-during their dissipation). In other words, the evolution can be directed "against the second law of thermodynamics" by forming patterns outside of equilibrium in the probability space. Due to that, a specie is not locked up in a certain pattern of behavior: it still can perform a variety of motions, and only the statistics of these motions is constrained by this pattern. It should be emphasized that such a "twist" is based upon the concept of reflection, i.e., the existence of the self-image (adopted from psychology). The model consists of a generator of stochastic processes which represents the motor dynamics in the form of nonlinear random walks, and a simulator of the nonlinear version of the diffusion
Dynamical Signatures of Living Systems
NASA Technical Reports Server (NTRS)
Zak, M.
1999-01-01
One of the main challenges in modeling living systems is to distinguish a random walk of physical origin (for instance, Brownian motions) from those of biological origin and that will constitute the starting point of the proposed approach. As conjectured, the biological random walk must be nonlinear. Indeed, any stochastic Markov process can be described by linear Fokker-Planck equation (or its discretized version), only that type of process has been observed in the inanimate world. However, all such processes always converge to a stable (ergodic or periodic) state, i.e., to the states of a lower complexity and high entropy. At the same time, the evolution of living systems directed toward a higher level of complexity if complexity is associated with a number of structural variations. The simplest way to mimic such a tendency is to incorporate a nonlinearity into the random walk; then the probability evolution will attain the features of diffusion equation: the formation and dissipation of shock waves initiated by small shallow wave disturbances. As a result, the evolution never "dies:" it produces new different configurations which are accompanied by an increase or decrease of entropy (the decrease takes place during formation of shock waves, the increase-during their dissipation). In other words, the evolution can be directed "against the second law of thermodynamics" by forming patterns outside of equilibrium in the probability space. Due to that, a specie is not locked up in a certain pattern of behavior: it still can perform a variety of motions, and only the statistics of these motions is constrained by this pattern. It should be emphasized that such a "twist" is based upon the concept of reflection, i.e., the existence of the self-image (adopted from psychology). The model consists of a generator of stochastic processes which represents the motor dynamics in the form of nonlinear random walks, and a simulator of the nonlinear version of the diffusion
Dynamic stability of maglev systems
Cai, Y.; Chen, S.S.; Mulcahy, T.M.; Rote, D.M.
1992-01-01
Since the occurrence of dynamic instabilities is not acceptable for any commercial maglev systems, it is important to consider the dynamic instability in the development of all maglev systems. This study is to consider the stability of maglev systems based on experimental data, scoping calculations and simple mathematical models. Divergence and flutter are obtained for coupled vibration of a three-degree-of-freedom maglev vehicle on the guideway which consists of double L-shaped aluminum segments attached to a rotating wheel. The theory and analysis developed in this study provides basic stability characteristics and identifies future research needs for maglev system.
Dynamic stability of maglev systems
Cai, Y.; Chen, S.S.; Mulcahy, T.M.; Rote, D.M.
1992-09-01
Since the occurrence of dynamic instabilities is not acceptable for any commercial maglev systems, it is important to consider the dynamic instability in the development of all maglev systems. This study is to consider the stability of maglev systems based on experimental data, scoping calculations and simple mathematical models. Divergence and flutter are obtained for coupled vibration of a three-degree-of-freedom maglev vehicle on the guideway which consists of double L-shaped aluminum segments attached to a rotating wheel. The theory and analysis developed in this study provides basic stability characteristics and identifies future research needs for maglev system.
Dynamic stability of maglev systems
Cai, Y.; Chen, S.S.; Mulcahy, T.M.; Rote, D.M.
1994-05-01
Because dynamic instabilities are not acceptable in any commercial maglev system, it is important to consider dynamic instability in the development of all maglev systems. This study considers the stability of maglev systems based on experimental data, scoping calculations, and simple mathematical models. Divergence and flutter are obtained for coupled vibration of a three-degree-of-freedom maglev vehicle on a guideway consisting of double L-shaped aluminum segments. The theory and analysis developed in this study provides basic stability characteristics and identifies future research needs for maglev systems.
Systoles in discrete dynamical systems
NASA Astrophysics Data System (ADS)
Fernandes, Sara; Grácio, Clara; Ramos, Carlos Correia
2013-01-01
The fruitful relationship between Geometry and Graph Theory has been explored by several authors benefiting also the Theory of discrete dynamical systems seen as Markov chains in graphs. In this work we will further explore the relation between these areas, giving a geometrical interpretation of notions from dynamical systems. In particular, we relate the topological entropy with the systole, here defined in the context of discrete dynamical systems. We show that for continuous interval maps the systole is trivial; however, for the class of interval maps with one discontinuity point the systole acquires relevance from the point of view of the dynamical behavior. Moreover, we define the geodesic length spectrum associated to a Markov interval map and we compute the referred spectrum in several examples.
NASA Astrophysics Data System (ADS)
Murray, Carl D.; Dermott, Stanley F.
2000-02-01
Preface; 1. Structure of the solar system; 2. The two-body problem; 3. The restricted three-body problem; 4. Tides, rotation and shape; 5. Spin-orbit coupling; 6. The disturbing function; 7. Secular perturbations; 8. Resonant perturbations; 9. Chaos and long-term evolution; 10. Planetary rings; Appendix A. Solar system data; Appendix B. Expansion of the disturbing function; Index.
Realization of dynamical electronic systems
NASA Astrophysics Data System (ADS)
Hammari, Elena; Catthoor, Francky; Iasemidis, Leonidas; Kjeldsberg, Per Gunnar; Huisken, Jos; Tsakalis, Konstantinos
2014-04-01
This article gives an overview of a methodology for building dynamical electronic systems. As an example a part of a system for epileptic seizure prediction is used, which monitors EEG signals and continuously calculates the largest short-term Lyapunov exponents. In dynamical electronic systems, the cost of exploitation, for instance energy consumption, may vary substantially with the values of input signals. In addition, the functions describing the variations are not known at the time the system is designed. As a result, the architecture of the system must accommodate for the worst case exploitation costs, which rapidly exceed the available resources (for instance battery life) when accumulated over time. The presented system scenario methodology solves these challenges by identifying at design time groups of possible exploitation costs, called system scenarios, and implementing a mechanism to detect system scenarios at run time and re-configure the system to cost-efficiently accommodate them. During reconfiguration, the optimized system architecture settings for the active system scenario are selected and the total exploitation cost is reduced. When the dynamic behavior is due to input data variables with a large number of possible values, current techniques for bottom-up scenario identification and detection becomes too complex. A new top-down technique, based on polygonal regions, is presented in this paper. The results for the example system indicate that with 10 system scenarios the average energy consumption of the system can be reduced by 28% and brought within 5% of the theoretically best solution.
Benchmarking novel approaches for modelling species range dynamics.
Zurell, Damaris; Thuiller, Wilfried; Pagel, Jörn; Cabral, Juliano S; Münkemüller, Tamara; Gravel, Dominique; Dullinger, Stefan; Normand, Signe; Schiffers, Katja H; Moore, Kara A; Zimmermann, Niklaus E
2016-08-01
Increasing biodiversity loss due to climate change is one of the most vital challenges of the 21st century. To anticipate and mitigate biodiversity loss, models are needed that reliably project species' range dynamics and extinction risks. Recently, several new approaches to model range dynamics have been developed to supplement correlative species distribution models (SDMs), but applications clearly lag behind model development. Indeed, no comparative analysis has been performed to evaluate their performance. Here, we build on process-based, simulated data for benchmarking five range (dynamic) models of varying complexity including classical SDMs, SDMs coupled with simple dispersal or more complex population dynamic models (SDM hybrids), and a hierarchical Bayesian process-based dynamic range model (DRM). We specifically test the effects of demographic and community processes on model predictive performance. Under current climate, DRMs performed best, although only marginally. Under climate change, predictive performance varied considerably, with no clear winners. Yet, all range dynamic models improved predictions under climate change substantially compared to purely correlative SDMs, and the population dynamic models also predicted reasonable extinction risks for most scenarios. When benchmarking data were simulated with more complex demographic and community processes, simple SDM hybrids including only dispersal often proved most reliable. Finally, we found that structural decisions during model building can have great impact on model accuracy, but prior system knowledge on important processes can reduce these uncertainties considerably. Our results reassure the clear merit in using dynamic approaches for modelling species' response to climate change but also emphasize several needs for further model and data improvement. We propose and discuss perspectives for improving range projections through combination of multiple models and for making these approaches
Innovations in dynamic test restraint systems
NASA Technical Reports Server (NTRS)
Fuld, Christopher J.
1990-01-01
Recent launch system development programs have led to a new generation of large scale dynamic tests. The variety of test scenarios share one common requirement: restrain and capture massive high velocity flight hardware with no structural damage. The Space Systems Lab of McDonnell Douglas developed a remarkably simple and cost effective approach to such testing using ripstitch energy absorbers adapted from the sport of technical rockclimbing. The proven system reliability of the capture system concept has led to a wide variety of applications in test system design and in aerospace hardware design.
NASA Technical Reports Server (NTRS)
Wisdom, Jack
1987-01-01
The rotational dynamics of irregularly shaped satellites and the origin of Kirkwood Gaps are discussed. The chaotic tumbling of Hyperion and the anomalously low eccentricity of Deimos are examined. The Digital Orrery is used to explore the phase space of the ellipic restricted three body problem near the principal commensurabilities (2/1, 5/2, 3/1, and 3/2). The results for the 3/1 commensurability are in close agreement with those found earlier with the algebraic mapping method. Large chaotic zones are associated with the 3/1, 2/1 and 5/2 resonances, where there are gaps in the distribution of asteroids. The region near the 3/2 resonance, where the Hilda group of asteroids is located, is largely devoid of chaotic behavior. Thus, there is a qualitative agreement between the character of the motion and the distribution of asteroids.
Systems Approach to Environmental Pollution.
ERIC Educational Resources Information Center
Chacko, George K., Ed.
The objective of a two-day Symposium on Systems Approach to Environmental Pollution of the Operations Research Society of America at the 137th Annual Meeting of the American Association for the Advancement of Science, December 27-28, 1970 in Chicago, Illinois, was not to raise the litany of a systems approach as the answer to all environmental…
Systems Approach to Environmental Pollution.
ERIC Educational Resources Information Center
Chacko, George K., Ed.
The objective of a two-day Symposium on Systems Approach to Environmental Pollution of the Operations Research Society of America at the 137th Annual Meeting of the American Association for the Advancement of Science, December 27-28, 1970 in Chicago, Illinois, was not to raise the litany of a systems approach as the answer to all environmental…
Time Discretization Approach to Dynamic Localization Conditions
NASA Astrophysics Data System (ADS)
Papp, E.
An alternative wavefunction to the description of the dynamic localization of a charged particle moving on a one-dimensional lattice under the influence of a periodic time dependent electric field is written down. For this purpose the method of characteristics such as applied by Dunlap and Kenkre [Phys. Rev. B 34, 3625 (1986)] has been modified by using a different integration variable. Handling this wavefunction one is faced with the selection of admissible time values. This results in a conditionally exactly solvable problem, now by accounting specifically for the implementation of a time discretization working in conjunction with a related dynamic localization condition. In addition, one resorts to the strong field limit, which amounts to replace, to leading order, the large order zeros of the Bessel function J0(z), used before in connection with the cosinusoidal modulation, by integral multiples of π. Here z stands for the ratio between the field amplitude and the frequency. The modulation function of the electric field vanishes on the nodal points of the time grid, which stands for an effective field-free behavior. This opens the way to propose quickly tractable dynamic localization conditions for arbitrary periodic modulations. We have also found that the present time discretization approach produces the minimization of the mean square displacement characterizing the usual exact wavefunction. Other realizations and comparisons have also been presented.
Dynamically Reconfigurable Approach to Multidisciplinary Problems
NASA Technical Reports Server (NTRS)
Alexandrov, Natalie M.; Lewis, Robert Michael
2003-01-01
The complexity and autonomy of the constituent disciplines and the diversity of the disciplinary data formats make the task of integrating simulations into a multidisciplinary design optimization problem extremely time-consuming and difficult. We propose a dynamically reconfigurable approach to MDO problem formulation wherein an appropriate implementation of the disciplinary information results in basic computational components that can be combined into different MDO problem formulations and solution algorithms, including hybrid strategies, with relative ease. The ability to re-use the computational components is due to the special structure of the MDO problem. We believe that this structure can and should be used to formulate and solve optimization problems in the multidisciplinary context. The present work identifies the basic computational components in several MDO problem formulations and examines the dynamically reconfigurable approach in the context of a popular class of optimization methods. We show that if the disciplinary sensitivity information is implemented in a modular fashion, the transfer of sensitivity information among the formulations under study is straightforward. This enables not only experimentation with a variety of problem formations in a research environment, but also the flexible use of formulations in a production design environment.
Chaotic transport in dynamical systems
NASA Astrophysics Data System (ADS)
Wiggins, Stephen
The subject of chaotic transport in dynamical systems is examined from the viewpoint of problems of phase space transport. The examples considered include uniform elliptical vortices in external linear time-dependent velocity fields; capture and passage through resonance in celestial mechanics; bubble dynamics in straining flows; and photodissociation of molecules. The discussion covers transport in two-dimensional maps; convective mixing and transport problems in fluid mechanics; transport in quasi-periodically forced systems; Markov models; and transport in k-degree-of-freedom Hamiltonian systems.
Dynamically reconfigurable photovoltaic system
Okandan, Murat; Nielson, Gregory N.
2016-12-27
A PV system composed of sub-arrays, each having a group of PV cells that are electrically connected to each other. A power management circuit for each sub-array has a communications interface and serves to connect or disconnect the sub-array to a programmable power grid. The power grid has bus rows and bus columns. A bus management circuit is positioned at a respective junction of a bus column and a bus row and is programmable through its communication interface to connect or disconnect a power path in the grid. As a result, selected sub-arrays are connected by selected power paths to be in parallel so as to produce a low system voltage, and, alternately in series so as to produce a high system voltage that is greater than the low voltage by at least a factor of ten.
Dynamically reconfigurable photovoltaic system
Okandan, Murat; Nielson, Gregory N.
2016-05-31
A PV system composed of sub-arrays, each having a group of PV cells that are electrically connected to each other. A power management circuit for each sub-array has a communications interface and serves to connect or disconnect the sub-array to a programmable power grid. The power grid has bus rows and bus columns. A bus management circuit is positioned at a respective junction of a bus column and a bus row and is programmable through its communication interface to connect or disconnect a power path in the grid. As a result, selected sub-arrays are connected by selected power paths to be in parallel so as to produce a low system voltage, and, alternately in series so as to produce a high system voltage that is greater than the low voltage by at least a factor of ten.
Constraint elimination in dynamical systems
NASA Technical Reports Server (NTRS)
Singh, R. P.; Likins, P. W.
1989-01-01
Large space structures (LSSs) and other dynamical systems of current interest are often extremely complex assemblies of rigid and flexible bodies subjected to kinematical constraints. A formulation is presented for the governing equations of constrained multibody systems via the application of singular value decomposition (SVD). The resulting equations of motion are shown to be of minimum dimension.
System Science approach to Space Weather forecast
NASA Astrophysics Data System (ADS)
Balikhin, Michael A.
There are many dynamical systems in nature that are so complex that mathematical models of their behaviour can not be deduced from first principles with the present level of our knowledge. Obvious examples are organic cell, human brain, etc often attract system scientists. A example that is closer to space physics is the terrestrial magnetosphere. The system approach has been developed to understand such complex objects from the observation of their dynamics. The systems approach employs advanced data analysis methodologies to identify patterns in the overall system behaviour and provides information regarding the linear and nonlinear processes involved in the dynamics of the system. This, in combination with the knowledge deduced from the first principles, creates the opportunity to find mathematical relationships that govern the evolution of a particular physical system. Advances and problems of systems science applications to provide a reliable forecasts of space weather phenomena such as geomagnetic storms, substorms and radiation belts particle fluxes are reviewed and compared with the physics based models.
A hierarchical state space approach to affective dynamics
Lodewyckx, Tom; Tuerlinckx, Francis; Kuppens, Peter; Allen, Nicholas; Sheeber, Lisa
2010-01-01
Linear dynamical system theory is a broad theoretical framework that has been applied in various research areas such as engineering, econometrics and recently in psychology. It quantifies the relations between observed inputs and outputs that are connected through a set of latent state variables. State space models are used to investigate the dynamical properties of these latent quantities. These models are especially of interest in the study of emotion dynamics, with the system representing the evolving emotion components of an individual. However, for simultaneous modeling of individual and population differences, a hierarchical extension of the basic state space model is necessary. Therefore, we introduce a Bayesian hierarchical model with random effects for the system parameters. Further, we apply our model to data that were collected using the Oregon adolescent interaction task: 66 normal and 67 depressed adolescents engaged in a conflict interaction with their parents and second-to-second physiological and behavioral measures were obtained. System parameters in normal and depressed adolescents were compared, which led to interesting discussions in the light of findings in recent literature on the links between cardiovascular processes, emotion dynamics and depression. We illustrate that our approach is flexible and general: The model can be applied to any time series for multiple systems (where a system can represent any entity) and moreover, one is free to focus on whatever component of the versatile model. PMID:21516216
Controlling fast chaos in delay dynamical systems.
Blakely, Jonathan N; Illing, Lucas; Gauthier, Daniel J
2004-05-14
We introduce a novel approach for controlling fast chaos in time-delay dynamical systems and use it to control a chaotic photonic device with a characteristic time scale of approximately 12 ns. Our approach is a prescription for how to implement existing chaos-control algorithms in a way that exploits the system's inherent time delay and allows control even in the presence of substantial control-loop latency (the finite time it takes signals to propagate through the components in the controller). This research paves the way for applications exploiting fast control of chaos, such as chaos-based communication schemes and stabilizing the behavior of ultrafast lasers.
Dispersive Time-Delay Dynamical Systems
NASA Astrophysics Data System (ADS)
Pimenov, Alexander; Slepneva, Svetlana; Huyet, Guillaume; Vladimirov, Andrei G.
2017-05-01
We present a theoretical approach to investigate the effect of dispersion in dynamical systems commonly described by time-delay models. The introduction of a polarization equation provides a means to introduce dispersion as a distributed delay term. The expansion of this term in power series, as usually performed to study the propagation of waves in spatially extended systems, can lead to the appearance of spurious instabilities. This approach is illustrated using a long cavity laser, where in the normal dispersion regime both the experiment and theory show a stable operation, while a modulation instability, commonly referred as the Benjamin-Feir instability, is observed in the anomalous dispersion regime.
Managing Complex Dynamical Systems
ERIC Educational Resources Information Center
Cox, John C.; Webster, Robert L.; Curry, Jeanie A.; Hammond, Kevin L.
2011-01-01
Management commonly engages in a variety of research designed to provide insight into the motivation and relationships of individuals, departments, organizations, etc. This paper demonstrates how the application of concepts associated with the analysis of complex systems applied to such data sets can yield enhanced insights for managerial action.
NASA Astrophysics Data System (ADS)
Schultz, A.; Lampitt, R. S.
2001-12-01
Advances in theoretical understanding of the natural systems in the sea and in the Earth below have been closely associated with new data sets made possible by technological advances. The plate tectonic revolution, the discovery of hydrothermal circulation, and many other examples can be attributed to the application of innovative new technology to the study of the sea. A consortium of research groups and institutions within the United Kingdom is planning a system of multidisciplinary ocean observatories to study the components of, and linkages between the physical, chemical and biological processes regulating the earth-ocean-atmosphere-biosphere system. An engineering feasibility design study has been completed which has resulted in a robust and flexible design for a telecommunications/power buoy system, and a UK NERC Thematic Programme is in the advanced planning stage. Representatives of the US, Japan, France, Portugal, Spain, Germany and other countries have been involved in consultations, and a coordinated international effort is expected to develop throughout the Atlantic and S Oceans, with collaborations extended to observatories operated by cooperating partners in other regions. The B-DEOS observatory system is designed to allow studies on scales of order cm to 1000 km, as well as to supplement on larger spatial scales the emerging global ocean and seafloor solid earth observatory network. The facility will make it possible to obtain requisite long-term synoptic baseline data, and to monitor natural and man-made changes to this system by: 1) Establishing a long-term, permanent and relocatable network of instrumented seafloor platforms, moorings and profiler vehicles, provided with power from the ocean surface and internal power supplies, and maintaining a real- or near-real time bidirectional Internet link to shore. 2) Examining the time varying properties of these different environments (solid earth, ocean, atmosphere, biosphere), exploring the links
A statistical state dynamics approach to wall turbulence
NASA Astrophysics Data System (ADS)
Farrell, B. F.; Gayme, D. F.; Ioannou, P. J.
2017-03-01
This paper reviews results obtained using statistical state dynamics (SSD) that demonstrate the benefits of adopting this perspective for understanding turbulence in wall-bounded shear flows. The SSD approach used in this work employs a second-order closure that retains only the interaction between the streamwise mean flow and the streamwise mean perturbation covariance. This closure restricts nonlinearity in the SSD to that explicitly retained in the streamwise constant mean flow together with nonlinear interactions between the mean flow and the perturbation covariance. This dynamical restriction, in which explicit perturbation-perturbation nonlinearity is removed from the perturbation equation, results in a simplified dynamics referred to as the restricted nonlinear (RNL) dynamics. RNL systems, in which a finite ensemble of realizations of the perturbation equation share the same mean flow, provide tractable approximations to the SSD, which is equivalent to an infinite ensemble RNL system. This infinite ensemble system, referred to as the stochastic structural stability theory system, introduces new analysis tools for studying turbulence. RNL systems provide computationally efficient means to approximate the SSD and produce self-sustaining turbulence exhibiting qualitative features similar to those observed in direct numerical simulations despite greatly simplified dynamics. The results presented show that RNL turbulence can be supported by as few as a single streamwise varying component interacting with the streamwise constant mean flow and that judicious selection of this truncated support or `band-limiting' can be used to improve quantitative accuracy of RNL turbulence. These results suggest that the SSD approach provides new analytical and computational tools that allow new insights into wall turbulence.
A statistical state dynamics approach to wall turbulence.
Farrell, B F; Gayme, D F; Ioannou, P J
2017-03-13
This paper reviews results obtained using statistical state dynamics (SSD) that demonstrate the benefits of adopting this perspective for understanding turbulence in wall-bounded shear flows. The SSD approach used in this work employs a second-order closure that retains only the interaction between the streamwise mean flow and the streamwise mean perturbation covariance. This closure restricts nonlinearity in the SSD to that explicitly retained in the streamwise constant mean flow together with nonlinear interactions between the mean flow and the perturbation covariance. This dynamical restriction, in which explicit perturbation-perturbation nonlinearity is removed from the perturbation equation, results in a simplified dynamics referred to as the restricted nonlinear (RNL) dynamics. RNL systems, in which a finite ensemble of realizations of the perturbation equation share the same mean flow, provide tractable approximations to the SSD, which is equivalent to an infinite ensemble RNL system. This infinite ensemble system, referred to as the stochastic structural stability theory system, introduces new analysis tools for studying turbulence. RNL systems provide computationally efficient means to approximate the SSD and produce self-sustaining turbulence exhibiting qualitative features similar to those observed in direct numerical simulations despite greatly simplified dynamics. The results presented show that RNL turbulence can be supported by as few as a single streamwise varying component interacting with the streamwise constant mean flow and that judicious selection of this truncated support or 'band-limiting' can be used to improve quantitative accuracy of RNL turbulence. These results suggest that the SSD approach provides new analytical and computational tools that allow new insights into wall turbulence.This article is part of the themed issue 'Toward the development of high-fidelity models of wall turbulence at large Reynolds number'.
This paper presents a methodology that combines the power of an Artificial Neural Network and Information Theory to forecast variables describing the condition of a regional system. The novelty and strength of this approach is in the application of Fisher information, a key metho...
This paper presents a methodology that combines the power of an Artificial Neural Network and Information Theory to forecast variables describing the condition of a regional system. The novelty and strength of this approach is in the application of Fisher information, a key metho...
Computational stability analysis of dynamical systems
NASA Astrophysics Data System (ADS)
Nikishkov, Yuri Gennadievich
2000-10-01
Due to increased available computer power, the analysis of nonlinear flexible multi-body systems, fixed-wing aircraft and rotary-wing vehicles is relying on increasingly complex, large scale models. An important aspect of the dynamic response of flexible multi-body systems is the potential presence of instabilities. Stability analysis is typically performed on simplified models with the smallest number of degrees of freedom required to capture the physical phenomena that cause the instability. The system stability boundaries are then evaluated using the characteristic exponent method or Floquet theory for systems with constant or periodic coefficients, respectively. As the number of degrees of freedom used to represent the system increases, these methods become increasingly cumbersome, and quickly unmanageable. In this work, a novel approach is proposed, the Implicit Floquet Analysis, which evaluates the largest eigenvalues of the transition matrix using the Arnoldi algorithm, without the explicit computation of this matrix. This method is far more computationally efficient than the classical approach and is ideally suited for systems involving a large number of degrees of freedom. The proposed approach is conveniently implemented as a postprocessing step to any existing simulation tool. The application of the method to a geometrically nonlinear multi-body dynamics code is presented. This work also focuses on the implementation of trimming algorithms and the development of tools for the graphical representation of numerical simulations and stability information for multi-body systems.
Data-driven approach to dynamic visual attention modelling
NASA Astrophysics Data System (ADS)
Culibrk, Dubravko; Sladojevic, Srdjan; Riche, Nicolas; Mancas, Matei; Crnojevic, Vladimir
2012-06-01
Visual attention deployment mechanisms allow the Human Visual System to cope with an overwhelming amount of visual data by dedicating most of the processing power to objects of interest. The ability to automatically detect areas of the visual scene that will be attended to by humans is of interest for a large number of applications, from video coding, video quality assessment to scene understanding. Due to this fact, visual saliency (bottom-up attention) models have generated significant scientific interest in recent years. Most recent work in this area deals with dynamic models of attention that deal with moving stimuli (videos) instead of traditionally used still images. Visual saliency models are usually evaluated against ground-truth eye-tracking data collected from human subjects. However, there are precious few recently published approaches that try to learn saliency from eyetracking data and, to the best of our knowledge, no approaches that try to do so when dynamic saliency is concerned. The paper attempts to fill this gap and describes an approach to data-driven dynamic saliency model learning. A framework is proposed that enables the use of eye-tracking data to train an arbitrary machine learning algorithm, using arbitrary features derived from the scene. We evaluate the methodology using features from a state-of-the art dynamic saliency model and show how simple machine learning algorithms can be trained to distinguish between visually salient and non-salient parts of the scene.
Similarity Metrics for Closed Loop Dynamic Systems
NASA Technical Reports Server (NTRS)
Whorton, Mark S.; Yang, Lee C.; Bedrossian, Naz; Hall, Robert A.
2008-01-01
To what extent and in what ways can two closed-loop dynamic systems be said to be "similar?" This question arises in a wide range of dynamic systems modeling and control system design applications. For example, bounds on error models are fundamental to the controller optimization with modern control design methods. Metrics such as the structured singular value are direct measures of the degree to which properties such as stability or performance are maintained in the presence of specified uncertainties or variations in the plant model. Similarly, controls-related areas such as system identification, model reduction, and experimental model validation employ measures of similarity between multiple realizations of a dynamic system. Each area has its tools and approaches, with each tool more or less suited for one application or the other. Similarity in the context of closed-loop model validation via flight test is subtly different from error measures in the typical controls oriented application. Whereas similarity in a robust control context relates to plant variation and the attendant affect on stability and performance, in this context similarity metrics are sought that assess the relevance of a dynamic system test for the purpose of validating the stability and performance of a "similar" dynamic system. Similarity in the context of system identification is much more relevant than are robust control analogies in that errors between one dynamic system (the test article) and another (the nominal "design" model) are sought for the purpose of bounding the validity of a model for control design and analysis. Yet system identification typically involves open-loop plant models which are independent of the control system (with the exception of limited developments in closed-loop system identification which is nonetheless focused on obtaining open-loop plant models from closed-loop data). Moreover the objectives of system identification are not the same as a flight test and
A Systems Approach to Teaching.
ERIC Educational Resources Information Center
Kelly, Robert E.
The systematic approach to teaching provides a method for the functional organization and development of instruction. This method applies to preparation of materials for classroom use, as well as for print and non-print media. Inputs to the systems approach include well defined objectives, analysis of the intended audience, special criteria…
Constraint Embedding Technique for Multibody System Dynamics
NASA Technical Reports Server (NTRS)
Woo, Simon S.; Cheng, Michael K.
2011-01-01
Multibody dynamics play a critical role in simulation testbeds for space missions. There has been a considerable interest in the development of efficient computational algorithms for solving the dynamics of multibody systems. Mass matrix factorization and inversion techniques and the O(N) class of forward dynamics algorithms developed using a spatial operator algebra stand out as important breakthrough on this front. Techniques such as these provide the efficient algorithms and methods for the application and implementation of such multibody dynamics models. However, these methods are limited only to tree-topology multibody systems. Closed-chain topology systems require different techniques that are not as efficient or as broad as those for tree-topology systems. The closed-chain forward dynamics approach consists of treating the closed-chain topology as a tree-topology system subject to additional closure constraints. The resulting forward dynamics solution consists of: (a) ignoring the closure constraints and using the O(N) algorithm to solve for the free unconstrained accelerations for the system; (b) using the tree-topology solution to compute a correction force to enforce the closure constraints; and (c) correcting the unconstrained accelerations with correction accelerations resulting from the correction forces. This constraint-embedding technique shows how to use direct embedding to eliminate local closure-loops in the system and effectively convert the system back to a tree-topology system. At this point, standard tree-topology techniques can be brought to bear on the problem. The approach uses a spatial operator algebra approach to formulating the equations of motion. The operators are block-partitioned around the local body subgroups to convert them into aggregate bodies. Mass matrix operator factorization and inversion techniques are applied to the reformulated tree-topology system. Thus in essence, the new technique allows conversion of a system with
Automated reverse engineering of nonlinear dynamical systems.
Bongard, Josh; Lipson, Hod
2007-06-12
Complex nonlinear dynamics arise in many fields of science and engineering, but uncovering the underlying differential equations directly from observations poses a challenging task. The ability to symbolically model complex networked systems is key to understanding them, an open problem in many disciplines. Here we introduce for the first time a method that can automatically generate symbolic equations for a nonlinear coupled dynamical system directly from time series data. This method is applicable to any system that can be described using sets of ordinary nonlinear differential equations, and assumes that the (possibly noisy) time series of all variables are observable. Previous automated symbolic modeling approaches of coupled physical systems produced linear models or required a nonlinear model to be provided manually. The advance presented here is made possible by allowing the method to model each (possibly coupled) variable separately, intelligently perturbing and destabilizing the system to extract its less observable characteristics, and automatically simplifying the equations during modeling. We demonstrate this method on four simulated and two real systems spanning mechanics, ecology, and systems biology. Unlike numerical models, symbolic models have explanatory value, suggesting that automated "reverse engineering" approaches for model-free symbolic nonlinear system identification may play an increasing role in our ability to understand progressively more complex systems in the future.
Insights into nuclear dynamics using live-cell imaging approaches.
Bigley, Rachel B; Payumo, Alexander Y; Alexander, Jeffrey M; Huang, Guo N
2017-03-01
The nucleus contains the genetic blueprint of the cell and myriad interactions within this subcellular structure are required for gene regulation. In the current scientific era, characterization of these gene regulatory networks through biochemical techniques coupled with systems-wide 'omic' approaches has become commonplace. However, these strategies are limited because they represent a mere snapshot of the cellular state. To obtain a holistic understanding of nuclear dynamics, relevant molecules must be studied in their native contexts in living systems. Live-cell imaging approaches are capable of providing quantitative assessment of the dynamics of gene regulatory interactions within the nucleus. We survey recent insights into what live-cell imaging approaches have provided the field of nuclear dynamics. In this review, we focus on interactions of DNA with other DNA loci, proteins, RNA, and the nuclear envelope. WIREs Syst Biol Med 2017, 9:e1372. doi: 10.1002/wsbm.1372 For further resources related to this article, please visit the WIREs website.
Dynamic mask: new approach to laser engraving of halftone images
NASA Astrophysics Data System (ADS)
Kadan, Victor N.; Pekarik, Alexander S.; Estrela Liopis, Rafael V.
1997-03-01
New approach to laser engraving of half tone images has been proposed and tested. Combining two basic approaches to laser engraving -- single pulse mask imaging and raster element construction by pack of laser pulses -- the new system constructs every individual raster element by imaging on the workpiece surface a dynamic mask of controlled size. The dynamic mask shape corresponds to the required raster element shape. This approach offers several important advantages over the conventional ones: (1) analog control of the mask shape provides gray level continuum, thus ensuring the image quality, unattainable by other means; (2) raster element marking by single laser pulse provides very good marking rate. It takes only one scan of the writing laser head to mark raster line. Much more powerful laser pulses can be used to engrave complete raster element by single pulse instead of its point-by-point construction by consecutive laser pulses; (3) the influence of laser beam quality parameters, such as beam divergence, and power instabilities on the gray level has been greatly reduced because raster element shape primarily depends on the mask shape and not on the power level and beam divergence. Dynamic mask system can be used both with cw and pulsed laser. Gray scale tones can be reproduced by the linear raster line width in the first case. Advantages of the new device have been demonstrated by engravings on stone, wood, etc. made with 50 W carbon-dioxide laser.
Nested observer for linear hybrid dynamical systems
Abdi, M.; Bensalah, H.; Cherki, B.
2009-03-05
The synthesis of observers for linear hybrid dynamical systems ''HDS,'' is significant from the point of view of the applications (control, diagnoses...); it is still, largely open. We proposed a new approach inspired from a new method of identification, where we could obtain better results with respect to discrimination between the discrete states in conflicts and time necessary to this latter. The results of the suggested technique proved to be satisfactory.
Waddington, Dynamic Systems, and Epigenetics
Tronick, Ed; Hunter, Richard G.
2016-01-01
Waddington coined the term “epigenetic” to attempt to explain the complex, dynamic interactions between the developmental environment and the genome that led to the production of phenotype. Waddington's thoughts on the importance of both adaptability and canalization of phenotypic development are worth recalling as well, as they emphasize the available range for epigenetic action and the importance of environmental feedback (or lack thereof) in the development of complex traits. We suggest that a dynamic systems view fits well with Waddington's conception of epigenetics in the developmental context, as well as shedding light on the study of the molecular epigenetic effects of the environment on brain and behavior. Further, the dynamic systems view emphasizes the importance of the multi-directional interchange between the organism, the genome and various aspects of the environment to the ultimate phenotype. PMID:27375447
A minimum principle for chaotic dynamical systems
NASA Astrophysics Data System (ADS)
Bracken, Paul; Góra, Paweł; Boyarsky, Abraham
2002-06-01
Discrete time dynamical systems generated by the iteration of nonlinear maps, such as the logistic map or the tent map, provide interesting examples of chaotic systems. But what is the physical principle behind the emergence of these maps? In the continuous time settings, differential equations of mechanics arise from the minimization of the energy function (Hamiltonian). However, there is no general physical principle for the discrete time analogue of differential equations, namely, maps. In this note, we present an approach to this problem. Using a natural definition of energy for chaotic systems, we minimize energy subject to the constraint that the observed dynamical system has a known entropy. We consider the case where the natural invariant measure is Lebesgue. Invoking the Euler-Lagrange equation, we derive a nonlinear second order differential equation whose solution is the chaotic map that minimizes energy.
A molecular dynamics approach to barrodiffusion
NASA Astrophysics Data System (ADS)
Cooley, James; Marciante, Mathieu; Murillo, Michael
2016-10-01
Unexpected phenomena in the reaction rates for Inertial Confinement Fusion (ICF) capsules have led to a renewed interest in the thermo-dynamically driven diffusion process for the past 10 years, often described collectively as barodiffusion. In the current context, barodiffusion would manifest as a process that separates ions of differing mass and charge ratios due to pressure and temperature gradients set-up through shock structures in the capsule core. Barrodiffusion includes additional mass transfer terms that account for the irreversible transport of species due to gradients in the system, both thermodynamic and electric e.g, i = - ρD [ ∇c +kp ∇ln(pi) +kT(i) ∇ln(Ti) +kt(e) ∇ln(Te) +eke/Ti ∇ϕ ] . Several groups have attacked this phenomena using continuum scale models and supplemented with kinetic theory to derive coefficients for the different diffusion terms based on assumptions about the collisional processes. In contrast, we have applied a molecular dynamics (MD) simulation to this system to gain a first-principle understanding of the rate kinetics and to assess the accuracy of the differin
Logical Attractors: a Boolean Approach to the Dynamics of Psychosis
NASA Astrophysics Data System (ADS)
Kupper, Z.; Hoffmann, H.
A Boolean modeling approach to attractors in the dynamics of psychosis is presented: Kinetic Logic, originating from R. Thomas, describes systems on an intermediate level between a purely verbal, qualitative description and a description using nonlinear differential equations. With this method we may model impact, feedback and temporal evolution, as well as analyze the resulting attractors. In our previous research the method has been applied to general and more specific questions in the dynamics of psychotic disorders. In this paper a model is introduced that describes different dynamical patterns of chronic psychosis in the context of vocational rehabilitation. It also shows to be useful in formulating and exploring possible treatment strategies. Finally, some of the limitations and benefits of Kinetic Logic as a modeling tool for psychology and psychiatry are discussed.
A novel similarity comparison approach for dynamic ECG series.
Yin, Hong; Zhu, Xiaoqian; Ma, Shaodong; Yang, Shuqiang; Chen, Liqian
2015-01-01
The heart sound signal is a reflection of heart and vascular system motion. Long-term continuous electrocardiogram (ECG) contains important information which can be helpful to prevent heart failure. A single piece of a long-term ECG recording usually consists of more than one hundred thousand data points in length, making it difficult to derive hidden features that may be reflected through dynamic ECG monitoring, which is also very time-consuming to analyze. In this paper, a Dynamic Time Warping based on MapReduce (MRDTW) is proposed to make prognoses of possible lesions in patients. Through comparison of a real-time ECG of a patient with the reference sets of normal and problematic cardiac waveforms, the experimental results reveal that our approach not only retains high accuracy, but also greatly improves the efficiency of the similarity measure in dynamic ECG series.
Percolation approach to glassy dynamics with continuously broken ergodicity.
Arenzon, Jeferson J; Coniglio, Antonio; Fierro, Annalisa; Sellitto, Mauro
2014-08-01
We show that the relaxation dynamics near a glass transition with continuous ergodicity breaking can be endowed with a geometric interpretation based on percolation theory. At the mean-field level this approach is consistent with the mode-coupling theory (MCT) of type-A liquid-glass transitions and allows one to disentangle the universal and nonuniversal contributions to MCT relaxation exponents. Scaling predictions for the time correlation function are successfully tested in the F(12) schematic model and facilitated spin systems on a Bethe lattice. Our approach immediately suggests the extension of MCT scaling laws to finite spatial dimensions and yields predictions for dynamic relaxation exponents below an upper critical dimension of 6.
Dynamics of Variable Mass Systems
NASA Technical Reports Server (NTRS)
Eke, Fidelis O.
1998-01-01
This report presents the results of an investigation of the effects of mass loss on the attitude behavior of spinning bodies in flight. The principal goal is to determine whether there are circumstances under which the motion of variable mass systems can become unstable in the sense that their transverse angular velocities become unbounded. Obviously, results from a study of this kind would find immediate application in the aerospace field. The first part of this study features a complete and mathematically rigorous derivation of a set of equations that govern both the translational and rotational motions of general variable mass systems. The remainder of the study is then devoted to the application of the equations obtained to a systematic investigation of the effect of various mass loss scenarios on the dynamics of increasingly complex models of variable mass systems. It is found that mass loss can have a major impact on the dynamics of mechanical systems, including a possible change in the systems stability picture. Factors such as nozzle geometry, combustion chamber geometry, propellant's initial shape, size and relative mass, and propellant location can all have important influences on the system's dynamic behavior. The relative importance of these parameters on-system motion are quantified in a way that is useful for design purposes.
Polymer Fluid Dynamics: Continuum and Molecular Approaches.
Bird, R B; Giacomin, A J
2016-06-07
To solve problems in polymer fluid dynamics, one needs the equations of continuity, motion, and energy. The last two equations contain the stress tensor and the heat-flux vector for the material. There are two ways to formulate the stress tensor: (a) One can write a continuum expression for the stress tensor in terms of kinematic tensors, or (b) one can select a molecular model that represents the polymer molecule and then develop an expression for the stress tensor from kinetic theory. The advantage of the kinetic theory approach is that one gets information about the relation between the molecular structure of the polymers and the rheological properties. We restrict the discussion primarily to the simplest stress tensor expressions or constitutive equations containing from two to four adjustable parameters, although we do indicate how these formulations may be extended to give more complicated expressions. We also explore how these simplest expressions are recovered as special cases of a more general framework, the Oldroyd 8-constant model. Studying the simplest models allows us to discover which types of empiricisms or molecular models seem to be worth investigating further. We also explore equivalences between continuum and molecular approaches. We restrict the discussion to several types of simple flows, such as shearing flows and extensional flows, which are of greatest importance in industrial operations. Furthermore, if these simple flows cannot be well described by continuum or molecular models, then it is not necessary to lavish time and energy to apply them to more complex flow problems.
A systems approach to obesity.
Lee, Bruce Y; Bartsch, Sarah M; Mui, Yeeli; Haidari, Leila A; Spiker, Marie L; Gittelsohn, Joel
2017-01-01
Obesity has become a truly global epidemic, affecting all age groups, all populations, and countries of all income levels. To date, existing policies and interventions have not reversed these trends, suggesting that innovative approaches are needed to transform obesity prevention and control. There are a number of indications that the obesity epidemic is a systems problem, as opposed to a simple problem with a linear cause-and-effect relationship. What may be needed to successfully address obesity is an approach that considers the entire system when making any important decision, observation, or change. A systems approach to obesity prevention and control has many benefits, including the potential to further understand indirect effects or to test policies virtually before implementing them in the real world. Discussed here are 5 key efforts to implement a systems approach for obesity prevention: 1) utilize more global approaches; 2) bring new experts from disciplines that do not traditionally work with obesity to share experiences and ideas with obesity experts; 3) utilize systems methods, such as systems mapping and modeling; 4) modify and combine traditional approaches to achieve a stronger systems orientation; and 5) bridge existing gaps between research, education, policy, and action. This article also provides an example of how a systems approach has been used to convene a multidisciplinary team and conduct systems mapping and modeling as part of an obesity prevention program in Baltimore, Maryland. © The Author(s) 2016. Published by Oxford University Press on behalf of the International Life Sciences Institute. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.
Energy efficiency of a dynamic glazing system
Lollini, R.; Danza, L.; Meroni, I.
2010-04-15
The reduction of air-conditioning energy consumptions is one of the main indicators to act on when improving the energy efficiency in buildings. In the case of advanced technological buildings, a meaningful contribution to the thermal loads and the energy consumptions reduction could depend on the correct configuration and management of the envelope systems. In recent years, the architectural trend toward highly transparent all-glass buildings presents a unique challenge and opportunity to advance the market for emerging, smart, dynamic window and dimmable daylighting control technologies (). A prototype dynamic glazing system was developed and tested at ITC-CNR; it is aimed at actively responding to the external environmental loads. Both an experimental campaign and analyses by theoretical models were carried out, aimed at evaluating the possible configurations depending on different weather conditions in several possible places. Therefore, the analytical models of the building-plant system were defined by using a dynamic energy simulation software (EnergyPlus). The variables that determine the system performance, also influenced by the boundary conditions, were analysed, such as U- and g-value; they concern both the morphology of the envelope system, such as dimensions, shading and glazing type, gap airflow thickness, in-gap airflow rate, and management, in terms of control algorithm parameters tuning fan and shading systems, as a function of the weather conditions. The configuration able to provide the best performances was finally identified by also assessing such performances, integrating the dynamic system in several building types and under different weather conditions. The dynamic envelope system prototype has become a commercial product with some applications in facade systems, curtain walls and windows. The paper describes the methodological approach to prototype development and the main results obtained, including simulations of possible applications on
Algebraic Structure of Dynamical Systems
2017-05-22
cryptography , computer science, and even biology. Viewed as a purely mathematical object, one can ask questions about the behavior of the dynamical system...6 Cryptography and Substitution Ciphers . . . . . . . . . . . . . . . . . . . . . . 7 3...associated with them. However, we will discuss how one of our main results can be applied to cryptography . In Section 3, we formulate three of our main
Elastica as a dynamical system
NASA Astrophysics Data System (ADS)
Bates, Larry; Chhabra, Robin; Śniatycki, Jędrzej
2016-12-01
The elastica is a curve in R3 that is stationary under variations of the integral of the square of the curvature. Elastica is viewed as a dynamical system that arises from the second order calculus of variations, and its quantization is discussed.
Gray, William G.; Miller, Cass T.
2010-01-01
This work is the eighth in a series that develops the fundamental aspects of the thermodynamically constrained averaging theory (TCAT) that allows for a systematic increase in the scale at which multiphase transport phenomena is modeled in porous medium systems. In these systems, the explicit locations of interfaces between phases and common curves, where three or more interfaces meet, are not considered at scales above the microscale. Rather, the densities of these quantities arise as areas per volume or length per volume. Modeling of the dynamics of these measures is an important challenge for robust models of flow and transport phenomena in porous medium systems, as the extent of these regions can have important implications for mass, momentum, and energy transport between and among phases, and formulation of a capillary pressure relation with minimal hysteresis. These densities do not exist at the microscale, where the interfaces and common curves correspond to particular locations. Therefore, it is necessary for a well-developed macroscale theory to provide evolution equations that describe the dynamics of interface and common curve densities. Here we point out the challenges and pitfalls in producing such evolution equations, develop a set of such equations based on averaging theorems, and identify the terms that require particular attention in experimental and computational efforts to parameterize the equations. We use the evolution equations developed to specify a closed two-fluid-phase flow model. PMID:21197134
Gray, William G; Miller, Cass T
2010-12-01
This work is the eighth in a series that develops the fundamental aspects of the thermodynamically constrained averaging theory (TCAT) that allows for a systematic increase in the scale at which multiphase transport phenomena is modeled in porous medium systems. In these systems, the explicit locations of interfaces between phases and common curves, where three or more interfaces meet, are not considered at scales above the microscale. Rather, the densities of these quantities arise as areas per volume or length per volume. Modeling of the dynamics of these measures is an important challenge for robust models of flow and transport phenomena in porous medium systems, as the extent of these regions can have important implications for mass, momentum, and energy transport between and among phases, and formulation of a capillary pressure relation with minimal hysteresis. These densities do not exist at the microscale, where the interfaces and common curves correspond to particular locations. Therefore, it is necessary for a well-developed macroscale theory to provide evolution equations that describe the dynamics of interface and common curve densities. Here we point out the challenges and pitfalls in producing such evolution equations, develop a set of such equations based on averaging theorems, and identify the terms that require particular attention in experimental and computational efforts to parameterize the equations. We use the evolution equations developed to specify a closed two-fluid-phase flow model.
Dynamic stability of maglev systems
Cai, Y.; Chen, S.S.; Mulcahy, T.M.; Rote, D.M.
1992-04-01
Because dynamic instability is not acceptable for any commercial maglev systems, it is important to consider this phenomenon in the development of all maglev systems. This study considers the stability of maglev systems based on experimental data, scoping calculations, and simple mathematical models. Divergence and flutter are obtained for coupled vibration of a three-degree-of-freedom maglev vehicle on a guideway consisting of double L-shaped aluminum segments attached to a rotating wheel. The theory and analysis developed in this study identifies basic stability characteristics and future research needs of maglev systems.
NASA Astrophysics Data System (ADS)
Nakai, Hiromi; Yoshikawa, Takeshi
2017-03-01
In this study, we developed an excited-state calculation method for large systems using dynamical polarizabilities at the time-dependent density functional theory level. Three equivalent theories, namely, coupled-perturbed self-consistent field (CPSCF), random phase approximation (RPA), and Green function (GF), were extended to linear-scaling methods using the divide-and-conquer (DC) technique. The implementations of the standard and DC-based CPSCF, RPA, and GF methods are described. Numerical applications of these methods to polyene chains, single-wall carbon nanotubes, and water clusters confirmed the accuracy and efficiency of the DC-based methods, especially DC-GF.
Nonlinear dynamical analysis and optimization for biological/biomedical systems.
Ben-Zvi, Amos; Lee, Jong Min
2009-01-01
As mathematical models are increasingly available for biological/biomedical systems, dynamic optimization can be a useful tool for manipulating systems. Dynamic optimization is a computational tool for finding a sequence of optimal actions to attain desired outcomes from the system. This chapter discusses two dynamic optimization algorithms, model predictive control and dynamic programming, in the context of finding optimal treatment strategy for correcting hypothalamic-pituitary-adrenal (HPA) axis dysfunction. It is shown that dynamic programming approach has the advantage over the model predictive control (MPC) methodology in terms of robustness to error in parameter estimates and flexibility of accommodating clinically relevant objective function.
Nonlinear Dynamics, Chaotic and Complex Systems
NASA Astrophysics Data System (ADS)
Infeld, E.; Zelazny, R.; Galkowski, A.
2011-04-01
Part I. Dynamic Systems Bifurcation Theory and Chaos: 1. Chaos in random dynamical systems V. M. Gunldach; 2. Controlling chaos using embedded unstable periodic orbits: the problem of optimal periodic orbits B. R. Hunt and E. Ott; 3. Chaotic tracer dynamics in open hydrodynamical flows G. Karolyi, A. Pentek, T. Tel and Z. Toroczkai; 4. Homoclinic chaos L. P. Shilnikov; Part II. Spatially Extended Systems: 5. Hydrodynamics of relativistic probability flows I. Bialynicki-Birula; 6. Waves in ionic reaction-diffusion-migration systems P. Hasal, V. Nevoral, I. Schreiber, H. Sevcikova, D. Snita, and M. Marek; 7. Anomalous scaling in turbulence: a field theoretical approach V. Lvov and I. Procaccia; 8. Abelian sandpile cellular automata M. Markosova; 9. Transport in an incompletely chaotic magnetic field F. Spineanu; Part III. Dynamical Chaos Quantum Physics and Foundations Of Statistical Mechanics: 10. Non-equilibrium statistical mechanics and ergodic theory L. A. Bunimovich; 11. Pseudochaos in statistical physics B. Chirikov; 12. Foundations of non-equilibrium statistical mechanics J. P. Dougherty; 13. Thermomechanical particle simulations W. G. Hoover, H. A. Posch, C. H. Dellago, O. Kum, C. G. Hoover, A. J. De Groot and B. L. Holian; 14. Quantum dynamics on a Markov background and irreversibility B. Pavlov; 15. Time chaos and the laws of nature I. Prigogine and D. J. Driebe; 16. Evolutionary Q and cognitive systems: dynamic entropies and predictability of evolutionary processes W. Ebeling; 17. Spatiotemporal chaos information processing in neural networks H. Szu; 18. Phase transitions and learning in neural networks C. Van den Broeck; 19. Synthesis of chaos A. Vanecek and S. Celikovsky; 20. Computational complexity of continuous problems H. Wozniakowski; Part IV. Complex Systems As An Interface Between Natural Sciences and Environmental Social and Economic Sciences: 21. Stochastic differential geometry in finance studies V. G. Makhankov; Part V. Conference Banquet
Architectural Analysis of Dynamically Reconfigurable Systems
NASA Technical Reports Server (NTRS)
Lindvall, Mikael; Godfrey, Sally; Ackermann, Chris; Ray, Arnab; Yonkwa, Lyly
2010-01-01
oTpics include: the problem (increased flexibility of architectural styles decrease analyzability, behavior emerges and varies depending on the configuration, does the resulting system run according to the intended design, and architectural decisions can impede or facilitate testing); top down approach to architecture analysis, detection of defects and deviations, and architecture and its testability; currently targeted projects GMSEC and CFS; analyzing software architectures; analyzing runtime events; actual architecture recognition; GMPUB in Dynamic SAVE; sample output from new approach; taking message timing delays into account; CFS examples of architecture and testability; some recommendations for improved testablity; and CFS examples of abstract interfaces and testability; CFS example of opening some internal details.
ERIC Educational Resources Information Center
Rosmawati
2014-01-01
Dynamic systems theory (DST) is presented in this article as a suitable approach to research the acquisition of second language (L2) because of its close alignment with the process of second language learning. Through a process of identifying and comparing the characteristics of a dynamic system with the process of L2 learning, this article…
ERIC Educational Resources Information Center
Rosmawati
2014-01-01
Dynamic systems theory (DST) is presented in this article as a suitable approach to research the acquisition of second language (L2) because of its close alignment with the process of second language learning. Through a process of identifying and comparing the characteristics of a dynamic system with the process of L2 learning, this article…
System learning approach to assess sustainability and ...
This paper presents a methodology that combines the power of an Artificial Neural Network and Information Theory to forecast variables describing the condition of a regional system. The novelty and strength of this approach is in the application of Fisher information, a key method in Information Theory, to preserve trends in the historical data and prevent over fitting projections. The methodology was applied to demographic, environmental, food and energy consumption, and agricultural production in the San Luis Basin regional system in Colorado, U.S.A. These variables are important for tracking conditions in human and natural systems. However, available data are often so far out of date that they limit the ability to manage these systems. Results indicate that the approaches developed provide viable tools for forecasting outcomes with the aim of assisting management toward sustainable trends. This methodology is also applicable for modeling different scenarios in other dynamic systems. Indicators are indispensable for tracking conditions in human and natural systems, however, available data is sometimes far out of date and limit the ability to gauge system status. Techniques like regression and simulation are not sufficient because system characteristics have to be modeled ensuring over simplification of complex dynamics. This work presents a methodology combining the power of an Artificial Neural Network and Information Theory to capture patterns in a real dyna
Global dynamic modeling of a transmission system
NASA Technical Reports Server (NTRS)
Choy, F. K.; Qian, W.
1993-01-01
The work performed on global dynamic simulation and noise correlation of gear transmission systems at the University of Akron is outlined. The objective is to develop a comprehensive procedure to simulate the dynamics of the gear transmission system coupled with the effects of gear box vibrations. The developed numerical model is benchmarked with results from experimental tests at NASA Lewis Research Center. The modal synthesis approach is used to develop the global transient vibration analysis procedure used in the model. Modal dynamic characteristics of the rotor-gear-bearing system are calculated by the matrix transfer method while those of the gear box are evaluated by the finite element method (NASTRAN). A three-dimensional, axial-lateral coupled bearing model is used to couple the rotor vibrations with the gear box motion. The vibrations between the individual rotor systems are coupled through the nonlinear gear mesh interactions. The global equations of motion are solved in modal coordinates and the transient vibration of the system is evaluated by a variable time-stepping integration scheme. The relationship between housing vibration and resulting noise of the gear transmission system is generated by linear transfer functions using experimental data. A nonlinear relationship of the noise components to the fundamental mesh frequency is developed using the hypercoherence function. The numerically simulated vibrations and predicted noise of the gear transmission system are compared with the experimental results from the gear noise test rig at NASA Lewis Research Center. Results of the comparison indicate that the global dynamic model developed can accurately simulate the dynamics of a gear transmission system.
Dynamics of immune system vulnerabilities
NASA Astrophysics Data System (ADS)
Stromberg, Sean P.
The adaptive immune system can be viewed as a complex system, which adapts, over time, to reflect the history of infections experienced by the organism. Understanding its operation requires viewing it in terms of tradeoffs under constraints and evolutionary history. It typically displays "robust, yet fragile" behavior, meaning common tasks are robust to small changes but novel threats or changes in environment can have dire consequences. In this dissertation we use mechanistic models to study several biological processes: the immune response, the homeostasis of cells in the lymphatic system, and the process that normally prevents autoreactive cells from entering the lymphatic system. Using these models we then study the effects of these processes interacting. We show that the mechanisms that regulate the numbers of cells in the immune system, in conjunction with the immune response, can act to suppress autoreactive cells from proliferating, thus showing quantitatively how pathogenic infections can suppress autoimmune disease. We also show that over long periods of time this same effect can thin the repertoire of cells that defend against novel threats, leading to an age correlated vulnerability. This vulnerability is shown to be a consequence of system dynamics, not due to degradation of immune system components with age. Finally, modeling a specific tolerance mechanism that normally prevents autoimmune disease, in conjunction with models of the immune response and homeostasis we look at the consequences of the immune system mistakenly incorporating pathogenic molecules into its tolerizing mechanisms. The signature of this dynamic matches closely that of the dengue virus system.
Research on Nonlinear Dynamical Systems.
1976-10-19
LaSalle , J .P ., “Stability theory and invariance principles ” , Dynamical Systems, An International Symposium, Vol.1, pp. 2 11—222 , Academic Press...1974 — 31 November 1975 Principal Investigator: Professor J. P. LaSalle Grant DAA G 29/76/G/0052 1 December 1975 - 31 August 1976 Principal...Investigator: Professor 3. P. LaSalle L.fsch.ts Cente r for. Dynamical Syst.m. Division of Appli.d Mathematics Brown Univ.r sity Providena., Rhod. ~~~~~ 02912 D
Dynamical systems probabilistic risk assessment
Denman, Matthew R.; Ames, Arlo Leroy
2014-03-01
Probabilistic Risk Assessment (PRA) is the primary tool used to risk-inform nuclear power regulatory and licensing activities. Risk-informed regulations are intended to reduce inherent conservatism in regulatory metrics (e.g., allowable operating conditions and technical specifications) which are built into the regulatory framework by quantifying both the total risk profile as well as the change in the risk profile caused by an event or action (e.g., in-service inspection procedures or power uprates). Dynamical Systems (DS) analysis has been used to understand unintended time-dependent feedbacks in both industrial and organizational settings. In dynamical systems analysis, feedback loops can be characterized and studied as a function of time to describe the changes to the reliability of plant Structures, Systems and Components (SSCs). While DS has been used in many subject areas, some even within the PRA community, it has not been applied toward creating long-time horizon, dynamic PRAs (with time scales ranging between days and decades depending upon the analysis). Understanding slowly developing dynamic effects, such as wear-out, on SSC reliabilities may be instrumental in ensuring a safely and reliably operating nuclear fleet. Improving the estimation of a plant's continuously changing risk profile will allow for more meaningful risk insights, greater stakeholder confidence in risk insights, and increased operational flexibility.
Mathematical simulation of Earth system dynamics
NASA Astrophysics Data System (ADS)
Dymnikov, V. P.; Lykosov, V. N.; Volodin, E. M.
2015-05-01
The mathematical simulation of the Earth system, the dynamics of which depends on physical, chemical, biological, and other processes and which requires interdisciplinary approaches to studying this problem, is considered. The term "the Earth system" extends the concept "the climatic system," since additional geospheres (lithosphere, heliosphere, etc.) are taken into account and a wider range of physical, chemical, biological, and social interactions is described. The present-day level of climate modeling is discussed, and some data obtained at the Institute of Numerical Mathematics, Russian Academy of Sciences (INM RAS), are presented for this purpose. The prospects for further development of climate models toward the creation of the Earth system models based on a seamless approach, according to which a unified model is used to make short-term (several days) and long-term (climatic) prediction, are considered.
Vehicle systems: coupled and interactive dynamics analysis
NASA Astrophysics Data System (ADS)
Vantsevich, Vladimir V.
2014-11-01
This article formulates a new direction in vehicle dynamics, described as coupled and interactive vehicle system dynamics. Formalised procedures and analysis of case studies are presented. An analytical consideration, which explains the physics of coupled system dynamics and its consequences for dynamics of a vehicle, is given for several sets of systems including: (i) driveline and suspension of a 6×6 truck, (ii) a brake mechanism and a limited slip differential of a drive axle and (iii) a 4×4 vehicle steering system and driveline system. The article introduces a formal procedure to turn coupled system dynamics into interactive dynamics of systems. A new research direction in interactive dynamics of an active steering and a hybrid-electric power transmitting unit is presented and analysed to control power distribution between the drive axles of a 4×4 vehicle. A control strategy integrates energy efficiency and lateral dynamics by decoupling dynamics of the two systems thus forming their interactive dynamics.
Network Physiology: How Organ Systems Dynamically Interact.
Bartsch, Ronny P; Liu, Kang K L; Bashan, Amir; Ivanov, Plamen Ch
2015-01-01
We systematically study how diverse physiologic systems in the human organism dynamically interact and collectively behave to produce distinct physiologic states and functions. This is a fundamental question in the new interdisciplinary field of Network Physiology, and has not been previously explored. Introducing the novel concept of Time Delay Stability (TDS), we develop a computational approach to identify and quantify networks of physiologic interactions from long-term continuous, multi-channel physiological recordings. We also develop a physiologically-motivated visualization framework to map networks of dynamical organ interactions to graphical objects encoded with information about the coupling strength of network links quantified using the TDS measure. Applying a system-wide integrative approach, we identify distinct patterns in the network structure of organ interactions, as well as the frequency bands through which these interactions are mediated. We establish first maps representing physiologic organ network interactions and discover basic rules underlying the complex hierarchical reorganization in physiologic networks with transitions across physiologic states. Our findings demonstrate a direct association between network topology and physiologic function, and provide new insights into understanding how health and distinct physiologic states emerge from networked interactions among nonlinear multi-component complex systems. The presented here investigations are initial steps in building a first atlas of dynamic interactions among organ systems.
Network Physiology: How Organ Systems Dynamically Interact
Bartsch, Ronny P.; Liu, Kang K. L.; Bashan, Amir; Ivanov, Plamen Ch.
2015-01-01
We systematically study how diverse physiologic systems in the human organism dynamically interact and collectively behave to produce distinct physiologic states and functions. This is a fundamental question in the new interdisciplinary field of Network Physiology, and has not been previously explored. Introducing the novel concept of Time Delay Stability (TDS), we develop a computational approach to identify and quantify networks of physiologic interactions from long-term continuous, multi-channel physiological recordings. We also develop a physiologically-motivated visualization framework to map networks of dynamical organ interactions to graphical objects encoded with information about the coupling strength of network links quantified using the TDS measure. Applying a system-wide integrative approach, we identify distinct patterns in the network structure of organ interactions, as well as the frequency bands through which these interactions are mediated. We establish first maps representing physiologic organ network interactions and discover basic rules underlying the complex hierarchical reorganization in physiologic networks with transitions across physiologic states. Our findings demonstrate a direct association between network topology and physiologic function, and provide new insights into understanding how health and distinct physiologic states emerge from networked interactions among nonlinear multi-component complex systems. The presented here investigations are initial steps in building a first atlas of dynamic interactions among organ systems. PMID:26555073
Dynamics of Polystylen (PS) Melts: Multi-Scale Molecular Dynamic(MD) Approach
NASA Astrophysics Data System (ADS)
Lee, Won Bo; Harmandaris, Vagelis; Fritz, Dominik; Kremer, Kurt
2009-03-01
Multi-scale approaches provide a systematic way to simulate much longer time and bigger systems, which allows us to study both large space and time scale problems. Dynamics of entangled polymer melts is one of those problems since it is always related to long time scales and large system sizes. Coarse- grained potentials of PS are obtained by multi-scale (atomistic to coarse-grained) MD approach. Time mapping (connection between atomistic and coarse-grained time units) is performed via matching mean square displacements of chain center of mass from both atomistic and coarse-grained simulations. One of interesting dynamic properties is stress autocorrelation functions (SAF) since they are directly related to physical properties of entangled polymer melts such as moduli, viscosities and entanglement lengths. SAF's of PS melts are evaluated by MD simulations. In order to reduce strong noise in SAF, we use time-averaged stresses, where averaging time is small enough to capture local chain relaxations.
Keystroke Dynamics-Based Credential Hardening Systems
NASA Astrophysics Data System (ADS)
Bartlow, Nick; Cukic, Bojan
abstract Keystroke dynamics are becoming a well-known method for strengthening username- and password-based credential sets. The familiarity and ease of use of these traditional authentication schemes combined with the increased trustworthiness associated with biometrics makes them prime candidates for application in many web-based scenarios. Our keystroke dynamics system uses Breiman’s random forests algorithm to classify keystroke input sequences as genuine or imposter. The system is capable of operating at various points on a traditional ROC curve depending on application-specific security needs. As a username/password authentication scheme, our approach decreases the system penetration rate associated with compromised passwords up to 99.15%. Beyond presenting results demonstrating the credential hardening effect of our scheme, we look into the notion that a user’s familiarity to components of a credential set can non-trivially impact error rates.
NASA Astrophysics Data System (ADS)
Hachay, O. A.; Khachay, O. Yu.
2009-04-01
Rock massif is an open dynamical system. We did an attempt to show the relation of our received earlier results with the developed physical and mathematical theory of the research of the state of the open dynamical conservative and dissipative systems to which relate also rock massive which are in the process of outworking. That thesis is presented quantitative with use of the phase portraits constructed with use of the phase coordinates as the parameters of the integral and interval intensity for the zones of heterogeneity of the second rank and their difference analogue of the time derivatives, which are defined by the use of active induction electromagnetic monitoring data. We provided re-search, which are set on the development of criterions for estimating the stability state of rock massive, using the 6- years electromagnetic and seismic data on two mines. The results lead to such conclusions: by the outworking of the concrete block of the massif the whole massif of the mine field has a change of the stress-deformed and phase states from one explosion to another, - the amount of absorbed and returned energy is not equal and therefore in the massif we see the energy storage,- the process of the energy returning develops with a time delay and depends very much from the gradient of the absorbed energy from high energy explosions,- in the massif occur zones of dynamical calm. That zones we can observe by the data of seismological monitoring - after the end of the minimum of the calm we have during one or two weeks till the moment of the technological gob caving to provide the space-time active electromagnetic or seismic monitoring for revealing the unstable zones of the second rank,-that zones can be after the explosion the sources of high energy dynamical events. That paper is devoted also to the analysis of the morphology of structure peculiarities of the disintegration zones before the high energy dynamical event. During the regular cycle of electromagnetic
Neural network approaches to dynamic collision-free trajectory generation.
Yang, S X; Meng, M
2001-01-01
In this paper, dynamic collision-free trajectory generation in a nonstationary environment is studied using biologically inspired neural network approaches. The proposed neural network is topologically organized, where the dynamics of each neuron is characterized by a shunting equation or an additive equation. The state space of the neural network can be either the Cartesian workspace or the joint space of multi-joint robot manipulators. There are only local lateral connections among neurons. The real-time optimal trajectory is generated through the dynamic activity landscape of the neural network without explicitly searching over the free space nor the collision paths, without explicitly optimizing any global cost functions, without any prior knowledge of the dynamic environment, and without any learning procedures. Therefore the model algorithm is computationally efficient. The stability of the neural network system is guaranteed by the existence of a Lyapunov function candidate. In addition, this model is not very sensitive to the model parameters. Several model variations are presented and the differences are discussed. As examples, the proposed models are applied to generate collision-free trajectories for a mobile robot to solve a maze-type of problem, to avoid concave U-shaped obstacles, to track a moving target and at the same to avoid varying obstacles, and to generate a trajectory for a two-link planar robot with two targets. The effectiveness and efficiency of the proposed approaches are demonstrated through simulation and comparison studies.
An innovations approach to decoupling of multibody dynamics and control
NASA Technical Reports Server (NTRS)
Rodriguez, G.
1989-01-01
The problem of hinged multibody dynamics is solved using an extension of the innovations approach of linear filtering and prediction theory to the problem of mechanical system modeling and control. This approach has been used quite effectively to diagonalize the equations for filtering and prediction for linear state space systems. It has similar advantages in the study of dynamics and control of multibody systems. The innovations approach advanced here consists of expressing the equations of motion in terms of two closely related processes: (1) the innovations process e, a sequence of moments, obtained from the applied moments T by means of a spatially recursive Kalman filter that goes from the tip of the manipulator to its base; (2) a residual process, a sequence of velocities, obtained from the joint-angle velocities by means of an outward smoothing operations. The innovations e and the applied moments T are related by means of the relationships e = (I - L)T and T = (I + K)e. The operation (I - L) is a causal lower triangular matrix which is generated by a spatially recursive Kalman filter and the corresponding discrete-step Riccati equation. Hence, the innovations and the applied moments can be obtained from each other by means of a causal operation which is itself casually invertible.
A mathematical approach to HIV infection dynamics
NASA Astrophysics Data System (ADS)
Ida, A.; Oharu, S.; Oharu, Y.
2007-07-01
In order to obtain a comprehensive form of mathematical models describing nonlinear phenomena such as HIV infection process and AIDS disease progression, it is efficient to introduce a general class of time-dependent evolution equations in such a way that the associated nonlinear operator is decomposed into the sum of a differential operator and a perturbation which is nonlinear in general and also satisfies no global continuity condition. An attempt is then made to combine the implicit approach (usually adapted for convective diffusion operators) and explicit approach (more suited to treat continuous-type operators representing various physiological interactions), resulting in a semi-implicit product formula. Decomposing the operators in this way and considering their individual properties, it is seen that approximation-solvability of the original model is verified under suitable conditions. Once appropriate terms are formulated to describe treatment by antiretroviral therapy, the time-dependence of the reaction terms appears, and such product formula is useful for generating approximate numerical solutions to the governing equations. With this knowledge, a continuous model for HIV disease progression is formulated and physiological interpretations are provided. The abstract theory is then applied to show existence of unique solutions to the continuous model describing the behavior of the HIV virus in the human body and its reaction to treatment by antiretroviral therapy. The product formula suggests appropriate discrete models describing the dynamics of host pathogen interactions with HIV1 and is applied to perform numerical simulations based on the model of the HIV infection process and disease progression. Finally, the results of our numerical simulations are visualized and it is observed that our results agree with medical and physiological aspects.
A systems approach to animal communication.
Hebets, Eileen A; Barron, Andrew B; Balakrishnan, Christopher N; Hauber, Mark E; Mason, Paul H; Hoke, Kim L
2016-03-16
Why animal communication displays are so complex and how they have evolved are active foci of research with a long and rich history. Progress towards an evolutionary analysis of signal complexity, however, has been constrained by a lack of hypotheses to explain similarities and/or differences in signalling systems across taxa. To address this, we advocate incorporating a systems approach into studies of animal communication--an approach that includes comprehensive experimental designs and data collection in combination with the implementation of systems concepts and tools. A systems approach evaluates overall display architecture, including how components interact to alter function, and how function varies in different states of the system. We provide a brief overview of the current state of the field, including a focus on select studies that highlight the dynamic nature of animal signalling. We then introduce core concepts from systems biology (redundancy, degeneracy, pluripotentiality, and modularity) and discuss their relationships with system properties (e.g. robustness, flexibility, evolvability). We translate systems concepts into an animal communication framework and accentuate their utility through a case study. Finally, we demonstrate how consideration of the system-level organization of animal communication poses new practical research questions that will aid our understanding of how and why animal displays are so complex.
A systems approach to animal communication
Barron, Andrew B.; Balakrishnan, Christopher N.; Hauber, Mark E.; Hoke, Kim L.
2016-01-01
Why animal communication displays are so complex and how they have evolved are active foci of research with a long and rich history. Progress towards an evolutionary analysis of signal complexity, however, has been constrained by a lack of hypotheses to explain similarities and/or differences in signalling systems across taxa. To address this, we advocate incorporating a systems approach into studies of animal communication—an approach that includes comprehensive experimental designs and data collection in combination with the implementation of systems concepts and tools. A systems approach evaluates overall display architecture, including how components interact to alter function, and how function varies in different states of the system. We provide a brief overview of the current state of the field, including a focus on select studies that highlight the dynamic nature of animal signalling. We then introduce core concepts from systems biology (redundancy, degeneracy, pluripotentiality, and modularity) and discuss their relationships with system properties (e.g. robustness, flexibility, evolvability). We translate systems concepts into an animal communication framework and accentuate their utility through a case study. Finally, we demonstrate how consideration of the system-level organization of animal communication poses new practical research questions that will aid our understanding of how and why animal displays are so complex. PMID:26936240
Dynamic combinatorial self-replicating systems.
Moulin, Emilie; Giuseppone, Nicolas
2012-01-01
Thanks to their intrinsic network topologies, dynamic combinatorial libraries (DCLs) represent new tools for investigating fundamental aspects related to self-organization and adaptation processes. Very recently the first examples integrating self-replication features within DCLs have pushed even further the idea of implementing dynamic combinatorial chemistry (DCC) towards minimal systems capable of self-construction and/or evolution. Indeed, feedback loop processes - in particular in the form of autocatalytic reactions - are keystones to build dynamic supersystems which could possibly approach the roots of "Darwinian" evolvability at mesoscale. This topic of current interest also shows significant potentialities beyond its fundamental character, because truly smart and autonomous materials for the future will have to respond to changes of their environment by selecting and by exponentially amplifying their fittest constituents.
NASA Astrophysics Data System (ADS)
Zañudo, Jorge G. T.; Albert, Réka
2013-06-01
Discrete dynamic models are a powerful tool for the understanding and modeling of large biological networks. Although a lot of progress has been made in developing analysis tools for these models, there is still a need to find approaches that can directly relate the network structure to its dynamics. Of special interest is identifying the stable patterns of activity, i.e., the attractors of the system. This is a problem for large networks, because the state space of the system increases exponentially with network size. In this work, we present a novel network reduction approach that is based on finding network motifs that stabilize in a fixed state. Notably, we use a topological criterion to identify these motifs. Specifically, we find certain types of strongly connected components in a suitably expanded representation of the network. To test our method, we apply it to a dynamic network model for a type of cytotoxic T cell cancer and to an ensemble of random Boolean networks of size up to 200. Our results show that our method goes beyond reducing the network and in most cases can actually predict the dynamical repertoire of the nodes (fixed states or oscillations) in the attractors of the system.
Hidden attractors in dynamical systems
NASA Astrophysics Data System (ADS)
Dudkowski, Dawid; Jafari, Sajad; Kapitaniak, Tomasz; Kuznetsov, Nikolay V.; Leonov, Gennady A.; Prasad, Awadhesh
2016-06-01
Complex dynamical systems, ranging from the climate, ecosystems to financial markets and engineering applications typically have many coexisting attractors. This property of the system is called multistability. The final state, i.e., the attractor on which the multistable system evolves strongly depends on the initial conditions. Additionally, such systems are very sensitive towards noise and system parameters so a sudden shift to a contrasting regime may occur. To understand the dynamics of these systems one has to identify all possible attractors and their basins of attraction. Recently, it has been shown that multistability is connected with the occurrence of unpredictable attractors which have been called hidden attractors. The basins of attraction of the hidden attractors do not touch unstable fixed points (if exists) and are located far away from such points. Numerical localization of the hidden attractors is not straightforward since there are no transient processes leading to them from the neighborhoods of unstable fixed points and one has to use the special analytical-numerical procedures. From the viewpoint of applications, the identification of hidden attractors is the major issue. The knowledge about the emergence and properties of hidden attractors can increase the likelihood that the system will remain on the most desirable attractor and reduce the risk of the sudden jump to undesired behavior. We review the most representative examples of hidden attractors, discuss their theoretical properties and experimental observations. We also describe numerical methods which allow identification of the hidden attractors.
Temporal dynamics of tunneling: Hydrodynamic approach
NASA Astrophysics Data System (ADS)
Dekel, G.; Fleurov, V.; Soffer, A.; Stucchio, C.
2007-04-01
We use the hydrodynamic representation of the Gross-Pitaevskii and nonlinear Schrödinger equations in order to analyze the dynamics of macroscopic tunneling processes. We observe a tendency to wave breaking and shock formation during the early stages of the tunneling process. A blip in the density distribution appears on the outskirts of the barrier and under proper conditions it may transform into a bright soliton. Our approach, based on the theory of shock formation in solutions of the Burgers equation, allows us to find the parameters of the ejected blip (or soliton if formed), including the velocity of its propagation. The blip in the density is formed regardless of the value and sign of the nonlinearity parameter. However, a soliton may be formed only if this parameter is negative (attraction) and large enough. A criterion is proposed. An ejection of a soliton is also observed numerically. We demonstrate, theoretically and numerically, controlled formation of a soliton through tunneling. The mass of the ejected soliton is controlled by the initial state.
Dynamic resource allocation in a hierarchical multiprocessor system: A preliminary study
NASA Technical Reports Server (NTRS)
Ngai, Tin-Fook
1986-01-01
An integrated system approach to dynamic resource allocation is proposed. Some of the problems in dynamic resource allocation and the relationship of these problems to system structures are examined. A general dynamic resource allocation scheme is presented. A hierarchial system architecture which dynamically maps between processor structure and programs at multiple levels of instantiations is described. Simulation experiments were conducted to study dynamic resource allocation on the proposed system. Preliminary evaluation based on simple dynamic resource allocation algorithms indicates that with the proposed system approach, the complexity of dynamic resource management could be significantly reduced while achieving reasonable effective dynamic resource allocation.
Computational fluid dynamics in ventilation: Practical approach
NASA Astrophysics Data System (ADS)
Fontaine, J. R.
The potential of computation fluid dynamics (CFD) for conceiving ventilation systems is shown through the simulation of five practical cases. The following examples are considered: capture of pollutants on a surface treating tank equipped with a unilateral suction slot in the presence of a disturbing air draft opposed to suction; dispersion of solid aerosols inside fume cupboards; performances comparison of two general ventilation systems in a silkscreen printing workshop; ventilation of a large open painting area; and oil fog removal inside a mechanical engineering workshop. Whereas the two first problems are analyzed through two dimensional numerical simulations, the three other cases require three dimensional modeling. For the surface treating tank case, numerical results are compared to laboratory experiment data. All simulations are carried out using EOL, a CFD software specially devised to deal with air quality problems in industrial ventilated premises. It contains many analysis tools to interpret the results in terms familiar to the industrial hygienist. Much experimental work has been engaged to validate the predictions of EOL for ventilation flows.
Dynamical Systems and Motion Vision.
1988-04-01
TASK Artificial Inteligence Laboratory AREA I WORK UNIT NUMBERS 545 Technology Square . Cambridge, MA 02139 C\\ II. CONTROLLING OFFICE NAME ANO0 ADDRESS...INSTITUTE OF TECHNOLOGY ARTIFICIAL INTELLIGENCE LABORATORY A.I.Memo No. 1037 April, 1988 Dynamical Systems and Motion Vision Joachim Heel Abstract: In this... Artificial Intelligence L3 Laboratory of the Massachusetts Institute of Technology. Support for the Laboratory’s [1 Artificial Intelligence Research is
From dynamical systems to renormalization
NASA Astrophysics Data System (ADS)
Menous, Frédéric
2013-09-01
In this paper we study logarithmic derivatives associated to derivations on completed graded Lie algebra, as well as the existence of inverses. These logarithmic derivatives, when invertible, generalize the exp-log correspondence between a Lie algebra and its Lie group. Such correspondences occur naturally in the study of dynamical systems when dealing with the linearization of vector fields and the non linearizability of a resonant vector fields corresponds to the non invertibility of a logarithmic derivative and to the existence of normal forms. These concepts, stemming from the theory of dynamical systems, can be rephrased in the abstract setting of Lie algebra and the same difficulties as in perturbative quantum field theory (pQFT) arise here. Surprisingly, one can adopt the same ideas as in pQFT with fruitful results such as new constructions of normal forms with the help of the Birkhoff decomposition. The analogy goes even further (locality of counter terms, choice of a renormalization scheme) and shall lead to more interactions between dynamical systems and quantum field theory.
From dynamical systems to renormalization
Menous, Frédéric
2013-09-15
In this paper we study logarithmic derivatives associated to derivations on completed graded Lie algebra, as well as the existence of inverses. These logarithmic derivatives, when invertible, generalize the exp-log correspondence between a Lie algebra and its Lie group. Such correspondences occur naturally in the study of dynamical systems when dealing with the linearization of vector fields and the non linearizability of a resonant vector fields corresponds to the non invertibility of a logarithmic derivative and to the existence of normal forms. These concepts, stemming from the theory of dynamical systems, can be rephrased in the abstract setting of Lie algebra and the same difficulties as in perturbative quantum field theory (pQFT) arise here. Surprisingly, one can adopt the same ideas as in pQFT with fruitful results such as new constructions of normal forms with the help of the Birkhoff decomposition. The analogy goes even further (locality of counter terms, choice of a renormalization scheme) and shall lead to more interactions between dynamical systems and quantum field theory.
Structural dynamics system model reduction
NASA Technical Reports Server (NTRS)
Chen, J. C.; Rose, T. L.; Wada, B. K.
1987-01-01
Loads analysis for structural dynamic systems is usually performed by finite element models. Because of the complexity of the structural system, the model contains large number of degree-of-freedom. The large model is necessary since details of the stress, loads and responses due to mission environments are computed. However, a simplified model is needed for other tasks such as pre-test analysis for modal testing, and control-structural interaction studies. A systematic method of model reduction for modal test analysis is presented. Perhaps it will be of some help in developing a simplified model for the control studies.
Research on Nonlinear Dynamical Systems.
1983-01-10
Professor J. P. LaSalle Grant DAAG29-79 C 0161 September 1, 1979 - September 24, 1982 Principal Investigators: H. T. Banks C. M. Dafermos J. K. Hale E...F. Infante J. P. LaSalle . J. Mallet-Paret Lefschetz Center for Dynamical Systems Division of Applied Mathematics D T I Brown University L emtc...publications LaSALLE , J.P. [94] Stability of nonautonomous systems, Journal of Nonlinear Analysis: Theory, Methods, and Applications, Vol.1, No.1
A System Dynamics Analysis of the Factors Affecting Combat Readiness
1980-06-01
experimental model approach to improving systems is the third foundation of system dynamics. The last foundation is the use of the digital computer to conduct...completion rate is a third order delay of the rated supplement requalification rate (RSRR). This delay represents the time period which is required...the relationships which exist in the combat readiness system, the third objective could be accomplished. The construction of a dynamic systems and
Cognitive Science, Representations and Dynamical Systems Theory
NASA Astrophysics Data System (ADS)
Haselager, W. F. G. (Pim); Bongers, Raoul M.; van Rooij, Iris
In this contribution we point out that the assumption of representation in the explanations and models of cognitive science has several disadvantages. We propose that the dynamical systems theory approach, emphasizing the embodied embedded nature of cognition, might provide an important, non-representational alternative. We stress the importance of the challenge, raised by Andy Clark (Clark & Toribio, 1994; Clark, 1997), to dynamical systems theory to deal with 'representation-hungry' cognitive tasks. We indicate a possible way to answer that challenge in a empirically applicable manner. We suggest that investigations of this kind strengthen a motto that can be used as an antidote to the traditional representational cravings of cognitive science: 'Don't use representations in explanation and modeling unless it is absolutely necessary.'
Classification framework for partially observed dynamical systems
NASA Astrophysics Data System (ADS)
Shen, Yuan; Tino, Peter; Tsaneva-Atanasova, Krasimira
2017-04-01
We present a general framework for classifying partially observed dynamical systems based on the idea of learning in the model space. In contrast to the existing approaches using point estimates of model parameters to represent individual data items, we employ posterior distributions over model parameters, thus taking into account in a principled manner the uncertainty due to both the generative (observational and/or dynamic noise) and observation (sampling in time) processes. We evaluate the framework on two test beds: a biological pathway model and a stochastic double-well system. Crucially, we show that the classification performance is not impaired when the model structure used for inferring posterior distributions is much more simple than the observation-generating model structure, provided the reduced-complexity inferential model structure captures the essential characteristics needed for the given classification task.
Dynamic security assessment processing system
NASA Astrophysics Data System (ADS)
Tang, Lei
The architecture of dynamic security assessment processing system (DSAPS) is proposed to address online dynamic security assessment (DSA) with focus of the dissertation on low-probability, high-consequence events. DSAPS upgrades current online DSA functions and adds new functions to fit into the modern power grid. Trajectory sensitivity analysis is introduced and its applications in power system are reviewed. An index is presented to assess transient voltage dips quantitatively using trajectory sensitivities. Then the framework of anticipatory computing system (ACS) for cascading defense is presented as an important function of DSAPS. ACS addresses various security problems and the uncertainties in cascading outages. Corrective control design is automated to mitigate the system stress in cascading progressions. The corrective controls introduced in the dissertation include corrective security constrained optimal power flow, a two-stage load control for severe under-frequency conditions, and transient stability constrained optimal power flow for cascading outages. With state-of-the-art computing facilities to perform high-speed extended-term time-domain simulation and optimization for large-scale systems, DSAPS/ACS efficiently addresses online DSA for low-probability, high-consequence events, which are not addressed by today's industrial practice. Human interference is reduced in the computationally burdensome analysis.
Network dynamics and systems biology
NASA Astrophysics Data System (ADS)
Norrell, Johannes A.
The physics of complex systems has grown considerably as a field in recent decades, largely due to improved computational technology and increased availability of systems level data. One area in which physics is of growing relevance is molecular biology. A new field, systems biology, investigates features of biological systems as a whole, a strategy of particular importance for understanding emergent properties that result from a complex network of interactions. Due to the complicated nature of the systems under study, the physics of complex systems has a significant role to play in elucidating the collective behavior. In this dissertation, we explore three problems in the physics of complex systems, motivated in part by systems biology. The first of these concerns the applicability of Boolean models as an approximation of continuous systems. Studies of gene regulatory networks have employed both continuous and Boolean models to analyze the system dynamics, and the two have been found produce similar results in the cases analyzed. We ask whether or not Boolean models can generically reproduce the qualitative attractor dynamics of networks of continuously valued elements. Using a combination of analytical techniques and numerical simulations, we find that continuous networks exhibit two effects---an asymmetry between on and off states, and a decaying memory of events in each element's inputs---that are absent from synchronously updated Boolean models. We show that in simple loops these effects produce exactly the attractors that one would predict with an analysis of the stability of Boolean attractors, but in slightly more complicated topologies, they can destabilize solutions that are stable in the Boolean approximation, and can stabilize new attractors. Second, we investigate ensembles of large, random networks. Of particular interest is the transition between ordered and disordered dynamics, which is well characterized in Boolean systems. Networks at the
Bridging developmental systems theory and evolutionary psychology using dynamic optimization.
Frankenhuis, Willem E; Panchanathan, Karthik; Clark Barrett, H
2013-07-01
Interactions between evolutionary psychologists and developmental systems theorists have been largely antagonistic. This is unfortunate because potential synergies between the two approaches remain unexplored. This article presents a method that may help to bridge the divide, and that has proven fruitful in biology: dynamic optimization. Dynamic optimization integrates developmental systems theorists' focus on dynamics and contingency with the 'design stance' of evolutionary psychology. It provides a theoretical framework as well as a set of tools for exploring the properties of developmental systems that natural selection might favor, given particular evolutionary ecologies. We also discuss limitations of the approach.
A dynamic programming approach to adaptive fractionation
NASA Astrophysics Data System (ADS)
Ramakrishnan, Jagdish; Craft, David; Bortfeld, Thomas; Tsitsiklis, John N.
2012-03-01
We conduct a theoretical study of various solution methods for the adaptive fractionation problem. The two messages of this paper are as follows: (i) dynamic programming (DP) is a useful framework for adaptive radiation therapy, particularly adaptive fractionation, because it allows us to assess how close to optimal different methods are, and (ii) heuristic methods proposed in this paper are near-optimal, and therefore, can be used to evaluate the best possible benefit of using an adaptive fraction size. The essence of adaptive fractionation is to increase the fraction size when the tumor and organ-at-risk (OAR) are far apart (a ‘favorable’ anatomy) and to decrease the fraction size when they are close together. Given that a fixed prescribed dose must be delivered to the tumor over the course of the treatment, such an approach results in a lower cumulative dose to the OAR when compared to that resulting from standard fractionation. We first establish a benchmark by using the DP algorithm to solve the problem exactly. In this case, we characterize the structure of an optimal policy, which provides guidance for our choice of heuristics. We develop two intuitive, numerically near-optimal heuristic policies, which could be used for more complex, high-dimensional problems. Furthermore, one of the heuristics requires only a statistic of the motion probability distribution, making it a reasonable method for use in a realistic setting. Numerically, we find that the amount of decrease in dose to the OAR can vary significantly (5-85%) depending on the amount of motion in the anatomy, the number of fractions and the range of fraction sizes allowed. In general, the decrease in dose to the OAR is more pronounced when: (i) we have a high probability of large tumor-OAR distances, (ii) we use many fractions (as in a hyper-fractionated setting) and (iii) we allow large daily fraction size deviations.
Statistical Mechanics of Dynamical Systems
NASA Astrophysics Data System (ADS)
Mori, H.; Hata, H.; Horita, T.; Kobayashi, T.
A statistical-mechanical formalism of chaos based on the geometry of invariant sets in phase space is discussed to show that chaotic dynamical systems can be treated by a formalism analogous to that of thermodynamic systems if one takes a relevant coarse-grained quantity, but their statistical laws are quite different from those of thermodynamic systems. This is a generalization of statistical mechanics for dealing with dissipative and hamiltonian (i.e., conservative) dynamical systems of a few degrees of freedom. Thus the sum of the local expansion rate of nearby orbits along relevant orbit over a long but finite time has been introduced in order to describe and characterize (1) a drastic change of the structure of a chaotic attractor at a bifurcation and anomalous phenomena associated, (2) a critical scaling of chaos in the neighborhood of a critical point for the bifurcation to a nonexotic state, and a self-similar temporal structure of a critical orbit on the critical 2^∞ attractor an the critical golden tori without mixing, (3) the critical KAM torus, diffusion and repeated sticking of a chaotic orbit to a critical torus in hamiltonian systems. Here a q-phase transition, analogous to the ferromagnetic phase transition, plays an important role. They are illustrated numerically and theoretically by treating the driven damped pendulum, the driven Duffing equation, the Henon map, and the dissipative and conservative standard maps. This description of chaos breaks the time-reversal symmetry of hamiltonian dynamical laws analogously to statistical mechanics of irreversible processes. The broken time-reversal symmetry is brought about by orbital instability of chaos.
Survivability of Deterministic Dynamical Systems
Hellmann, Frank; Schultz, Paul; Grabow, Carsten; Heitzig, Jobst; Kurths, Jürgen
2016-01-01
The notion of a part of phase space containing desired (or allowed) states of a dynamical system is important in a wide range of complex systems research. It has been called the safe operating space, the viability kernel or the sunny region. In this paper we define the notion of survivability: Given a random initial condition, what is the likelihood that the transient behaviour of a deterministic system does not leave a region of desirable states. We demonstrate the utility of this novel stability measure by considering models from climate science, neuronal networks and power grids. We also show that a semi-analytic lower bound for the survivability of linear systems allows a numerically very efficient survivability analysis in realistic models of power grids. Our numerical and semi-analytic work underlines that the type of stability measured by survivability is not captured by common asymptotic stability measures. PMID:27405955
Passive dynamic controllers for nonlinear mechanical systems
NASA Technical Reports Server (NTRS)
Juang, Jer-Nan; Wu, Shih-Chin; Phan, Minh; Longman, Richard W.
1991-01-01
A methodology for model-independant controller design for controlling large angular motion of multi-body dynamic systems is outlined. The controlled system may consist of rigid and flexible components that undergo large rigid body motion and small elastic deformations. Control forces/torques are applied to drive the system and at the same time suppress the vibration due to flexibility of the components. The proposed controller consists of passive second-order systems which may be designed with little knowledge of the system parameter, even if the controlled system is nonlinear. Under rather general assumptions, the passive design assures that the closed loop system has guaranteed stability properties. Unlike positive real controller design, stabilization can be accomplished without direct velocity feedback. In addition, the second-order passive design allows dynamic feedback controllers with considerable freedom to tune for desired system response, and to avoid actuator saturation. After developing the basic mathematical formulation of the design methodology, simulation results are presented to illustrate the proposed approach to a flexible six-degree-of-freedom manipulator.
Building America Systems Engineering Approach
2011-12-15
The Building America Research Teams use a systems engineering approach to achieve higher quality and energy savings in homes. Using these techniques, the energy consumption of new houses can be reduced by 40% or more with little or no impact on the cost of ownership.
Institutional Planning: A Systems Approach.
ERIC Educational Resources Information Center
Adamson, Willie D.
This four-chapter report explores the possible contributions of a systems approach to institutional planning. After introductory comments, Chapter I reviews the management theory of Henry Fayol, which emphasizes management tasks, such as planning, organizing, commanding, coordinating, and controlling, which are "universal" regardless of the level…
Dynamics systems vs. optimal control--a unifying view.
Schaal, Stefan; Mohajerian, Peyman; Ijspeert, Auke
2007-01-01
In the past, computational motor control has been approached from at least two major frameworks: the dynamic systems approach and the viewpoint of optimal control. The dynamic system approach emphasizes motor control as a process of self-organization between an animal and its environment. Nonlinear differential equations that can model entrainment and synchronization behavior are among the most favorable tools of dynamic systems modelers. In contrast, optimal control approaches view motor control as the evolutionary or development result of a nervous system that tries to optimize rather general organizational principles, e.g., energy consumption or accurate task achievement. Optimal control theory is usually employed to develop appropriate theories. Interestingly, there is rather little interaction between dynamic systems and optimal control modelers as the two approaches follow rather different philosophies and are often viewed as diametrically opposing. In this paper, we develop a computational approach to motor control that offers a unifying modeling framework for both dynamic systems and optimal control approaches. In discussions of several behavioral experiments and some theoretical and robotics studies, we demonstrate how our computational ideas allow both the representation of self-organizing processes and the optimization of movement based on reward criteria. Our modeling framework is rather simple and general, and opens opportunities to revisit many previous modeling results from this novel unifying view.
Free response approach in a parametric system
NASA Astrophysics Data System (ADS)
Huang, Dishan; Zhang, Yueyue; Shao, Hexi
2017-07-01
In this study, a new approach to predict the free response in a parametric system is investigated. It is proposed in the special form of a trigonometric series with an exponentially decaying function of time, based on the concept of frequency splitting. By applying harmonic balance, the parametric vibration equation is transformed into an infinite set of homogeneous linear equations, from which the principal oscillation frequency can be computed, and all coefficients of harmonic components can be obtained. With initial conditions, arbitrary constants in a general solution can be determined. To analyze the computational accuracy and consistency, an approach error function is defined, which is used to assess the computational error in the proposed approach and in the standard numerical approach based on the Runge-Kutta algorithm. Furthermore, an example of a dynamic model of airplane wing flutter on a turbine engine is given to illustrate the applicability of the proposed approach. Numerical solutions show that the proposed approach exhibits high accuracy in mathematical expression, and it is valuable for theoretical research and engineering applications of parametric systems.
Novel approach to dynamic modeling of active optical instruments
NASA Astrophysics Data System (ADS)
Wilhelm, Rainer; Johann, Ulrich A.
1999-08-01
The presented work is a versatile approach to time-dependent numerical modeling of active optical instruments. Based on a hybrid geometrical- and physical optics propagation code an optical modeling tool (OMT) has been developed. Mainly targeting at the simulation of astronomical telescopes it allows building linear and non-linear optical models for integration into dynamic end-to-end simulation environments with models for mechanical structure, control systems and various disturbances. The light propagation through an instrument is modeled by a sequence of polarization ray tracing and diffraction propagations. A radiometry algorithm based on a triangle grid interconnecting the rays computes the calibrated power flux. Recently the OMT has been implemented as an optical kernel within the End-to-End Model for the Very Large Telescope Interferometer (VLTI) developed at the European Southern Observatory. There it performs the dynamic computation of the electric field in the exit pupils of the VLTI including polarization, radiometry and diffraction effects.
Assessing order-(N) approach to flexible multibody dynamics
NASA Astrophysics Data System (ADS)
Hu, Tsay-Hsin G.; Mordfin, Theodore G.; Singh, Sudeep; Singh, Anil; Kumar, Manoj
1992-08-01
An efficient simulation has been developed to analyze the dynamics and control of spacecraft comprised of multiple flexible articulating bodies. The implementation employs a typical order-(N) multibody dynamics approach coupled with a state-of-the-art symbolic equation optimization algorithm. The relationship among computational time, system topology, number of the bodies and number of modes per body is empirically determined. For practical application in a CHAIN topology, the computational time is proportional to NB exp 1.3 NM exp 1.85, where NB is the number of bodies, and NM is the number of modes per body. Applied to the analysis of Space Station Freedom, which has a TREE topology, the order of the method is demonstrated to be proportional to NM exp A, where A varies from 1.4 to 2.0.