Journal articles on the topic 'Feedback dynamics'
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Song, Ki-Young, Madan M. Gupta, and Noriyasu Homma. "Design of an Error-Based Adaptive Controller for a Flexible Robot Arm Using Dynamic Pole Motion Approach." Journal of Robotics 2011 (2011): 1–9. http://dx.doi.org/10.1155/2011/726807.
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Design of an adaptive controller for complex dynamic systems is a big challenge faced by the researchers. In this paper, we introduce a novel concept ofdynamic pole motion(DPM) for the design of an error-based adaptive controller (E-BAC). The purpose of this novel design approach is to make the system response reasonably fast with no overshoot, where the system may be time varying and nonlinear with only partially known dynamics. The E-BAC is implanted in a system as a nonlinear controller with two dominant dynamic parameters: the dynamic position feedback and the dynamic velocity feedback. For illustrating the strength of this new approach, in this paper we give an example of a flexible robot with nonlinear dynamics. In the design of this feedback adaptive controller, parameters of the controller are designed as a function of the system error. The position feedbackKp(e,t)and the velocity feedbackKv(e,t)are continuously varying and formulated as a function of the system errore(t). This approach for formulating the adaptive controller yields a very fast response with no overshoot.
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Snippe, H. P., and J. H. van Hateren. "Dynamics of Nonlinear Feedback Control." Neural Computation 19, no. 5 (May 2007): 1179–214. http://dx.doi.org/10.1162/neco.2007.19.5.1179.
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Feedback control in neural systems is ubiquitous. Here we study the mathematics of nonlinear feedback control. We compare models in which the input is multiplied by a dynamic gain (multiplicative control) with models in which the input is divided by a dynamic attenuation (divisive control). The gain signal (resp. the attenuation signal) is obtained through a concatenation of an instantaneous nonlinearity and a linear low-pass filter operating on the output of the feedback loop. For input steps, the dynamics of gain and attenuation can be very different, depending on the mathematical form of the nonlinearity and the ordering of the nonlinearity and the filtering in the feedback loop. Further, the dynamics of feedback control can be strongly asymmetrical for increment versus decrement steps of the input. Nevertheless, for each of the models studied, the nonlinearity in the feedback loop can be chosen such that immediately after an input step, the dynamics of feedback control is symmetric with respect to increments versus decrements. Finally, we study the dynamics of the output of the control loops and find conditions under which overshoots and undershoots of the output relative to the steady-state output occur when the models are stimulated with low-pass filtered steps. For small steps at the input, overshoots and undershoots of the output do not occur when the filtering in the control path is faster than the low-pass filtering at the input. For large steps at the input, however, results depend on the model, and for some of the models, multiple overshoots and undershoots can occur even with a fast control path.
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Varone, A., A. Politi, and M. Ciofini. "CO2laser dynamics with feedback." Physical Review A 52, no. 4 (October 1, 1995): 3176–82. http://dx.doi.org/10.1103/physreva.52.3176.
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Wang, Xin, Zhiming Zheng, and Feng Fu. "Steering eco-evolutionary game dynamics with manifold control." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 476, no. 2233 (January 2020): 20190643. http://dx.doi.org/10.1098/rspa.2019.0643.
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Feedback loops between population dynamics of individuals and their ecological environment are ubiquitously found in nature and have shown profound effects on the resulting eco-evolutionary dynamics. By incorporating linear environmental feedback law into the replicator dynamics of two-player games, recent theoretical studies have shed light on understanding the oscillating dynamics of the social dilemma. However, the detailed effects of more general nonlinear feedback loops in multi-player games, which are more common especially in microbial systems, remain unclear. Here, we focus on ecological public goods games with environmental feedbacks driven by a nonlinear selection gradient. Unlike previous models, multiple segments of stable and unstable equilibrium manifolds can emerge from the population dynamical systems. We find that a larger relative asymmetrical feedback speed for group interactions centred on cooperators not only accelerates the convergence of stable manifolds but also increases the attraction basin of these stable manifolds. Furthermore, our work offers an innovative manifold control approach: by designing appropriate switching control laws, we are able to steer the eco-evolutionary dynamics to any desired population state. Our mathematical framework is an important generalization and complement to coevolutionary game dynamics, and also fills the theoretical gap in guiding the widespread problem of population state control in microbial experiments.
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Byrne, Michael P., and Tapio Schneider. "Atmospheric Dynamics Feedback: Concept, Simulations, and Climate Implications." Journal of Climate 31, no. 8 (March 26, 2018): 3249–64. http://dx.doi.org/10.1175/jcli-d-17-0470.1.
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AbstractThe regional climate response to radiative forcing is largely controlled by changes in the atmospheric circulation. It has been suggested that global climate sensitivity also depends on the circulation response, an effect called the “atmospheric dynamics feedback.” Using a technique to isolate the influence of changes in atmospheric circulation on top-of-the-atmosphere radiation, the authors calculate the atmospheric dynamics feedback in coupled climate models. Large-scale circulation changes contribute substantially to all-sky and cloud feedbacks in the tropics but are relatively less important at higher latitudes. Globally averaged, the atmospheric dynamics feedback is positive and amplifies the near-surface temperature response to climate change by an average of 8% in simulations with coupled models. A constraint related to the atmospheric mass budget results in the dynamics feedback being small on large scales relative to feedbacks associated with thermodynamic processes. Idealized-forcing simulations suggest that circulation changes at high latitudes are potentially more effective at influencing global temperature than circulation changes at low latitudes, and the implications for past and future climate change are discussed.
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Song, Tingting, Yiyuan Xie, Yichen Ye, Bocheng Liu, Junxiong Chai, Xiao Jiang, and Yanli Zheng. "Numerical Analysis of Nonlinear Dynamics Based on Spin-VCSELs with Optical Feedback." Photonics 8, no. 1 (January 4, 2021): 10. http://dx.doi.org/10.3390/photonics8010010.
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In this paper, the nonlinear dynamics of a novel model based on optically pumped spin-polarized vertical-cavity surface-emitting lasers (spin-VCSELs) with optical feedback is investigated numerically. Due to optical feedback being the external disturbance component, the complex nonlinear dynamical behaviors can be enhanced and the regions of different nonlinear dynamics in size can be extended with appropriate parameters of spin-VCSELs. According to the equations of the modified spin-flip model (SFM), the comparison of bifurcation diagrams is first presented for the clear presentation of different routes to chaos. Meanwhile, numerous bifurcation diagrams in color are illustrated to demonstrate the rich dynamical regimes intuitively, and the crucial effects of optical feedback strength, feedback delay, linewidth enhancement factor, and spin-flip relaxation rate on the region evolvement of complex dynamics of the proposed model are revealed to investigate the dependence of dynamical behaviors on external and internal parameters when the optical feedback scheme is introduced. These parameters play a remarkable role in enhancing the mechanism of complex dynamic oscillations. Furthermore, utilizing combination with time series, power spectra, and phase portraits, the various dynamical behaviors observed in the bifurcation diagram are simulated numerically. Correspondingly, the powerful measure 0–1 test is employed to distinguish between chaos and non-chaos.
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Zhang, Li Nan, Shu Xin Wang, Jian Min Li, and Jin Hua Li. "Design of a Master Manipulator with Dynamical Simplification for Master-Slave Robot." Applied Mechanics and Materials 418 (September 2013): 3–9. http://dx.doi.org/10.4028/www.scientific.net/amm.418.3.
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Dynamic behavior is an important factor to affect the performance of surgical robot, especially force-feedback master manipulator. In this paper, a force-feedback master manipulator with parallelogram is developed, which can realize self-gravity balance; Compare the dynamics of the force-feedback master manipulator with parallelogram mechanism and another one without parallelogram mechanism. The result shows that the dynamical equation of the master manipulator with parallelogram mechanism is simpler than the one without parallelogram mechanism. This parallelogram mechanism can be generally used in all the mechanical design that is needed to simplify the dynamics.
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Delire, Christine, Nathalie de Noblet-Ducoudré, Adriana Sima, and Isabelle Gouirand. "Vegetation Dynamics Enhancing Long-Term Climate Variability Confirmed by Two Models." Journal of Climate 24, no. 9 (May 1, 2011): 2238–57. http://dx.doi.org/10.1175/2010jcli3664.1.
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Abstract Two different coupled climate–vegetation models, the Community Climate Model version 3 coupled to the Integrated Biosphere Simulator (CCM3–IBIS) and the Laboratoire de Météorologie Dynamique’s climate model coupled to the Organizing Carbon and Hydrology in Dynamic Ecosystems model (LMDz–ORCHIDEE), are used to study the effects of vegetation dynamics on climate variability. Two sets of simulations of the preindustrial climate are performed using fixed climatological sea surface temperatures: one set taking into account vegetation cover dynamics and the other keeping the vegetation cover fixed. Spectral analysis of the simulated precipitation and temperature over land shows that for both models the interactions between vegetation dynamics and the atmosphere enhance the low-frequency variability of the biosphere–atmosphere system at time scales ranging from a few years to a century. Despite differences in the magnitude of the signal between the two models, this confirms that vegetation dynamics introduces a long-term memory into the climate system by slowly modifying the physical characteristics of the land surface (albedo, roughness evapotranspiration). Unrealistic modeled feedbacks between the vegetation and the atmosphere would cast doubts on this result. The simulated feedback processes in the models used in this work are compared to the observed using a recently developed statistical approach. The models simulate feedbacks of the right sign and order of magnitude over large regions of the globe: positive temperature feedback in the mid- to high latitudes, negative feedback in semiarid regions, and positive precipitation feedback in semiarid regions. The models disagree in the tropics, where there is no statistical significance in the observations. The realistic modeled vegetation–atmosphere feedback gives us confidence that the vegetation dynamics enhancement of the long-term climate variability is not a model artifact.
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Wang, Xiang-Hui, Zheng-Mao Wu, Zai-Fu Jiang, and Guang-Qiong Xia. "Nonlinear Dynamics of Two-State Quantum Dot Lasers under Optical Feedback." Photonics 8, no. 8 (July 27, 2021): 300. http://dx.doi.org/10.3390/photonics8080300.
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A modified rate equation model was presented to theoretically investigate the nonlinear dynamics of solitary two-state quantum dot lasers (TSQDLs) under optical feedback. The simulated results showed that, for a TSQDL biased at a relatively high current, the ground-state (GS) and excited-state (ES) lasing of the TSQDL can be stimulated simultaneously. After introducing optical feedback, both GS lasing and ES lasing can exhibit rich nonlinear dynamic states including steady state (S), period one (P1), period two (P2), multi-period (MP), and chaotic (C) state under different feedback strength and phase offset, respectively, and the dynamic states for the two lasing types are always identical. Furthermore, the influences of the linewidth enhancement factor (LEF) on the nonlinear dynamical state distribution of TSQDLs in the parameter space of feedback strength and phase offset were also analyzed. For a TSQDL with a larger LEF, much more dynamical states can be observed, and the parameter regions for two lasing types operating at chaotic state are widened after introducing optical feedback.
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Sejas, Sergio A., Ming Cai, Aixue Hu, Gerald A. Meehl, Warren Washington, and Patrick C. Taylor. "Individual Feedback Contributions to the Seasonality of Surface Warming." Journal of Climate 27, no. 14 (July 10, 2014): 5653–69. http://dx.doi.org/10.1175/jcli-d-13-00658.1.
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Abstract Using the climate feedback response analysis method, the authors examine the individual contributions of the CO2 radiative forcing and climate feedbacks to the magnitude, spatial pattern, and seasonality of the transient surface warming response in a 1% yr−1 CO2 increase simulation of the NCAR Community Climate System Model, version 4 (CCSM4). The CO2 forcing and water vapor feedback warm the surface everywhere throughout the year. The tropical warming is predominantly caused by the CO2 forcing and water vapor feedback, while the evaporation feedback reduces the warming. Most feedbacks exhibit noticeable seasonal variations; however, their net effect has little seasonal variation due to compensating effects, which keeps the tropical warming relatively invariant all year long. The polar warming has a pronounced seasonal cycle, with maximum warming in fall/winter and minimum warming in summer. In summer, the large cancelations between the shortwave and longwave cloud feedbacks and between the surface albedo feedback warming and the cooling from the ocean heat storage/dynamics feedback lead to a warming minimum. In polar winter, surface albedo and shortwave cloud feedbacks are nearly absent due to a lack of insolation. However, the ocean heat storage feedback relays the polar warming due to the surface albedo feedback from summer to winter, and the longwave cloud feedback warms the polar surface. Therefore, the seasonal variations in the cloud feedback, surface albedo feedback, and ocean heat storage/dynamics feedback, directly caused by the strong annual cycle of insolation, contribute primarily to the large seasonal variation of polar warming. Furthermore, the CO2 forcing and water vapor and atmospheric dynamics feedbacks add to the maximum polar warming in fall/winter.
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Park, Hye Jin, and Chaitanya S. Gokhale. "Ecological feedback on diffusion dynamics." Royal Society Open Science 6, no. 2 (February 2019): 181273. http://dx.doi.org/10.1098/rsos.181273.
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Spatial patterns are ubiquitous across different scales of organization in ecological systems. Animal coat pattern, spatial organization of insect colonies and vegetation in arid areas are prominent examples from such diverse ecologies. Typically, pattern formation has been described by reaction–diffusion equations, which consider individuals dispersing between subpopulations of a global pool. This framework applied to public goods game nicely showed the endurance of populations via diffusion and generation of spatial patterns. However, how the spatial characteristics, such as diffusion, are related to the eco-evolutionary process as well as the nature of the feedback from evolution to ecology and vice versa, has been so far neglected. We present a thorough analysis of the ecologically driven evolutionary dynamics in a spatially extended version of ecological public goods games. Furthermore, we show how these evolutionary dynamics feed back into shaping the ecology, thus together determining the fate of the system.
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De Jong, Menno, and Dietha Rijnks. "Dynamics of Iterative Reader Feedback." Journal of Business and Technical Communication 20, no. 2 (April 2006): 159–76. http://dx.doi.org/10.1177/1050651905284401.
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Kowitz, Gerald T., and Jay C. Smith. "The dynamics of successful feedback." Performance + Instruction 24, no. 8 (October 1985): 4–6. http://dx.doi.org/10.1002/pfi.4150240803.
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QIU, HUAHAI, and TIANSHOU ZHOU. "FEEDBACK-INDUCED COMPLEX DYNAMICS IN A TWO-COMPONENT REGULATORY CIRCUIT." International Journal of Bifurcation and Chaos 22, no. 03 (March 2012): 1250059. http://dx.doi.org/10.1142/s0218127412500599.
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Coupled positive and negative feedback loops form an essential building block of cellular signaling pathways, but the dynamics of such a system remain to be fully explored. Here, we systematically analyze a two-component circuit with interlinked positive and negative feedback loops, focusing on feedback-induced dynamics and their mechanisms. We show that feedbacks can induce monostability, oscillation, and excitability as well as the coexistence of two attractors (including that of two different stable steady states (called Type-I bistability) and that of both a stable steady state and a stable limit cycle (called Type-II bistability)). In particular for Type-II bistability, we find that feedback-controlled molecular noise can induce stochastic switching between two different attractors, and that the first passage time between them exhibits a multi-peak distribution. These investigations provide insights for understanding the biological functions of coupled positive and negative feedback circuits from the viewpoint of dynamics.
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VAIRAPPAN, CATHERINE, SHANGCE GAO, ZHENG TANG, and HIROKI TAMURA. "ANNEALED CHAOTIC LEARNING FOR TIME SERIES PREDICTION IN IMPROVED NEURO-FUZZY NETWORK WITH FEEDBACKS." International Journal of Computational Intelligence and Applications 08, no. 04 (December 2009): 429–44. http://dx.doi.org/10.1142/s1469026809002680.
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A new version of neuro-fuzzy system of feedbacks with chaotic dynamics is proposed in this work. Unlike the conventional neuro-fuzzy, improved neuro-fuzzy system with feedbacks is better able to handle temporal data series. By introducing chaotic dynamics into the feedback neuro-fuzzy system, the system has richer and more flexible dynamics to search for near-optimal solutions. In the experimental results, performance and effectiveness of the presented approach are evaluated by using benchmark data series. Comparison with other existing methods shows the proposed method for the neuro-fuzzy feedback is able to predict the time series accurately.
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Bishop, Laura, Freya Bailes, and Roger T. Dean. "Performing Musical Dynamics." Music Perception 32, no. 1 (September 1, 2014): 51–66. http://dx.doi.org/10.1525/mp.2014.32.1.51.
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Musicians anticipate and monitor the expressive effects of their actions during performance. Previous research suggests that the ability to imagine desired outcomes can partially compensate when auditory feedback is absent, permitting continued performance even though information about whether these outcomes are realized is unavailable. Research also suggests that musical imagery ability improves with increasing musical expertise. This study tested the hypothesis that expert musicians’ superior imagery abilities enable reduced reliance on auditory feedback, relative to novice musicians, during the performance of loudness changes (i.e., dynamics). Musicians reproduced the dynamic changes of sounded scales using a loudness slider as the availability of imagery and auditory feedback was manipulated. Contrary to expectations, only novices showed impairment in performing dynamics during imagery disruption and auditory feedback deprivation. Experts showed limited dependence on both sources of information, suggesting greater flexibility in how musical information is mentally represented, compared to novices, and an improved ability to adapt planning strategies.
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Simpson, Isla R., Theodore G. Shepherd, Peter Hitchcock, and John F. Scinocca. "Southern Annular Mode Dynamics in Observations and Models. Part II: Eddy Feedbacks." Journal of Climate 26, no. 14 (July 12, 2013): 5220–41. http://dx.doi.org/10.1175/jcli-d-12-00495.1.
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Abstract Many global climate models (GCMs) have trouble simulating southern annular mode (SAM) variability correctly, particularly in the Southern Hemisphere summer season where it tends to be too persistent. In this two-part study, a suite of experiments with the Canadian Middle Atmosphere Model (CMAM) is analyzed to improve the understanding of the dynamics of SAM variability and its deficiencies in GCMs. Here, an examination of the eddy–mean flow feedbacks is presented by quantification of the feedback strength as a function of zonal scale and season using a new methodology that accounts for intraseasonal forcing of the SAM. In the observed atmosphere, in the summer season, a strong negative feedback by planetary-scale waves, in particular zonal wavenumber 3, is found in a localized region in the southwest Pacific. It cancels a large proportion of the positive feedback by synoptic- and smaller-scale eddies in the zonal mean, resulting in a very weak overall eddy feedback on the SAM. CMAM is deficient in this negative feedback by planetary-scale waves, making a substantial contribution to its bias in summertime SAM persistence. Furthermore, this bias is not alleviated by artificially improving the climatological circulation, suggesting that climatological circulation biases are not the cause of the planetary wave feedback deficiency in the model. Analysis of the summertime eddy feedbacks in the models from phase 5 of the Coupled Model Intercomparison Project (CMIP5) confirms that this is indeed a common problem among GCMs, suggesting that understanding this planetary wave feedback and the reason for its deficiency in GCMs is key to improving the fidelity of simulated SAM variability in the summer season.
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Tran, Thanh T. "Feedback linearization and backstepping: an equivalence in control design of strict-feedback form." IMA Journal of Mathematical Control and Information 37, no. 4 (October 15, 2019): 1049–69. http://dx.doi.org/10.1093/imamci/dnz024.
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Abstract This paper investigates an equivalence between feedback linearization and backstepping control. Implications from equivalence are that stability and performance properties of one method are the same for another method. Thus, a property known to exist only for one method could be used to prove property also holds for another. Also, a suspected advantage of one method over the other could be proven to be a false conjecture. Control laws in both approaches are achieved by coordinate transformations and non-linear feedbacks. Further, resulting non-linear feedback control law achieved by feedback linearization method matches exactly with non-linear controller achieved by the backstepping control design. This equivalence is a general analytical match within the specific class of non-linear dynamic systems under investigation. Demonstrations are considered and validated via flight control of longitudinal dynamics of a high performance aircraft simulation model. Algorithms are tested and evaluated with analytical models and non-linear closed-loop simulation.
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Kayacan, Erkan, Zeki Y. Bayraktaroglu, and Wouter Saeys. "Modeling and control of a spherical rolling robot: a decoupled dynamics approach." Robotica 30, no. 4 (August 8, 2011): 671–80. http://dx.doi.org/10.1017/s0263574711000956.
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SUMMARYThis paper presents the results of a study on the dynamical modeling, analysis, and control of a spherical rolling robot. The rolling mechanism consists of a 2-DOF pendulum located inside a spherical shell with freedom to rotate about the transverse and longitudinal axis. The kinematics of the model has been investigated through the classical methods with rotation matrices. Dynamic modeling of the system is based on the Euler–Lagrange formalism. Nonholonomic and highly nonlinear equations of motion have then been decomposed into two simpler subsystems through the decoupled dynamics approach. A feedback linearization loop with fuzzy controllers has been designed for the control of the decoupled dynamics. Rolling of the controlled mechanism over linear and curvilinear trajectories has been simulated by using the proposed decoupled dynamical model and feedback controllers. Analysis of radius of curvature over curvilinear trajectories has also been investigated.
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Zimmermann, Florian. "The Dynamics of Motivated Beliefs." American Economic Review 110, no. 2 (February 1, 2020): 337–63. http://dx.doi.org/10.1257/aer.20180728.
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A key question in the literature on motivated reasoning and self-deception is how motivated beliefs are sustained in the presence of feedback. In this paper, we explore dynamic motivated belief patterns after feedback. We establish that positive feedback has a persistent effect on beliefs. Negative feedback, instead, influences beliefs in the short run, but this effect fades over time. We investigate the mechanisms of this dynamic pattern, and provide evidence for an asymmetry in the recall of feedback. Finally, we establish that, in line with theoretical accounts, incentives for belief accuracy mitigate the role of motivated reasoning. (JEL C91, D83, D91)
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Baillieul, J. "Chaotic dynamics and nonlinear feedback control." Banach Center Publications 14, no. 1 (1985): 17–34. http://dx.doi.org/10.4064/-14-1-17-34.
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Alitto, Henry J., and W. Martin Usrey. "Dissecting the Dynamics of Corticothalamic Feedback." Neuron 86, no. 3 (May 2015): 605–7. http://dx.doi.org/10.1016/j.neuron.2015.04.016.
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D'Lauro, C., Y. Xu, R. Kass, and M. J. Tarr. "Dynamics of feedback-driven visual learning." Journal of Vision 11, no. 11 (September 23, 2011): 1002. http://dx.doi.org/10.1167/11.11.1002.
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Cuddington, K., W. G. Wilson, and A. Hastings. "Ecosystem Engineers: Feedback and Population Dynamics." American Naturalist 173, no. 4 (April 2009): 488–98. http://dx.doi.org/10.1086/597216.
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Allahverdyan, A. E., and G. Mahler. "Employing feedback in adiabatic quantum dynamics." EPL (Europhysics Letters) 84, no. 4 (November 2008): 40007. http://dx.doi.org/10.1209/0295-5075/84/40007.
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Bauer, H. U., and T. Geisel. "Nonlinear dynamics of feedback multilayer perceptrons." Physical Review A 42, no. 4 (August 1, 1990): 2401–9. http://dx.doi.org/10.1103/physreva.42.2401.
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Chaves, Madalena, Daniel Figueiredo, and Manuel A. Martins. "Boolean dynamics revisited through feedback interconnections." Natural Computing 19, no. 1 (October 25, 2018): 29–49. http://dx.doi.org/10.1007/s11047-018-9716-8.
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Naganuma, Tomoya, Harpartap Singh, and Seiichiro Nakabayashi. "Feedback effect on pitting corrosion dynamics." Journal of Solid State Electrochemistry 19, no. 11 (August 16, 2015): 3219–28. http://dx.doi.org/10.1007/s10008-015-2991-8.
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Shell, Karen M., and Richard C. J. Somerville. "A Generalized Energy Balance Climate Model with Parameterized Dynamics and Diabatic Heating." Journal of Climate 18, no. 11 (June 1, 2005): 1753–72. http://dx.doi.org/10.1175/jcli3373.1.
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Abstract Energy balance models have proven useful in understanding mechanisms and feedbacks in the climate system. An original global energy balance model is presented here. The model is solved numerically for equilibrium climate states defined by zonal average temperature as a function of latitude for both a surface and an atmospheric layer. The effects of radiative, latent, and sensible heating are parameterized. The model includes a variable lapse rate and parameterizations of the major dynamical mechanisms responsible for meridional heat transport: the Hadley cell, midlatitude baroclinic eddies, and ocean circulation. The model reproduces both the mean variation of temperature with latitude and the global average heat budget within the uncertainty of observations. The utility of the model is demonstrated through examination of various climate feedbacks. One important feedback is the effect of the lapse rate on climate. When the planet warms as a result of an increase in the solar constant, the lapse rate acts as a negative feedback, effectively enhancing the longwave emission efficiency of the atmosphere. The lapse rate is also responsible for an increase in global average temperature when the meridional heat transport effectiveness is increased. The water vapor feedback enhances temperature changes, while the latent and sensible heating feedback reduces surface temperature changes.
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Yanase, Wataru, and Ayako Abe-Ouchi. "A Numerical Study on the Atmospheric Circulation over the Midlatitude North Pacific during the Last Glacial Maximum." Journal of Climate 23, no. 1 (January 1, 2010): 135–51. http://dx.doi.org/10.1175/2009jcli3148.1.
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Abstract The dynamics of the atmospheric circulation change over the midlatitude North Pacific under the boundary conditions during the last glacial maximum (LGM) have been studied by atmospheric general circulation models (GCMs) with different ocean feedbacks. Three boundary conditions in the LGM were different from those of the present day (PD): ice sheet with elevated topography and high albedo, atmospheric CO2 concentration, and insolation. The ocean component was treated as follows: a full-circulation ocean with dynamical and thermal ocean feedback [coupled general circulation model (CGCM)]; a slab ocean only with thermal feedback used to calculate the surface heat balance [slab ocean GCM (SGCM)]; and no ocean feedback by fixing sea surface temperature (SST) with pure atmospheric dynamics (AGCM). Both CGCM and SGCM simulated a weakened Pacific high pressure system in boreal summer during the LGM compared to the PD and an intensified Aleutian low pressure system in winter. Both in summer and winter, therefore, the lower-tropospheric circulation during the LGM showed midlatitude North Pacific cyclonic anomalies (NPCAs). To understand the dynamics determining the NPCAs, the sensitivity of the atmospheric response to the three boundary conditions were examined using the SGCM. It was shown that the high albedo of the ice sheet over North America was the dominant factor behind the NPCAs in both summer and winter. The ocean thermal feedback in winter played an essential role in the formation of the NPCA through SST change, while the ocean thermal feedback in summer and ocean dynamical feedback played secondary roles in the intensification of the NPCA. Possible mechanisms were inferred from the common features related to the NPCA formation in the experiments. In summer, the midlatitude NPCA was associated with the reduced land–ocean contrast of diabatic heating between the North Pacific and North America, which is consistent with theoretical studies on the mechanism for formation of subtropical high pressure systems. In winter, on the other hand, the anomaly of the SST gradient at midlatitude is thought to result in the NPCA through the modulation of heat and momentum transport in the storm track. The small (large) sensitivity of the NPCA formation to the ocean feedbacks in summer (winter) explains the strong (weak) consistency among the previous GCM experiments. Since the NPCAs are consistent with some geological records, the present study should be informative in understanding the actual dynamics of the LGM climate change.
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SIETTOS, CONSTANTINOS I., IOANNIS G. KEVREKIDIS, and DIMITRIOS MAROUDAS. "COARSE BIFURCATION DIAGRAMS VIA MICROSCOPIC SIMULATORS: A STATE-FEEDBACK CONTROL-BASED APPROACH." International Journal of Bifurcation and Chaos 14, no. 01 (January 2004): 207–20. http://dx.doi.org/10.1142/s0218127404009193.
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We present and illustrate a feedback control-based framework that enables microscopic/stochastic simulators to trace their "coarse" bifurcation diagrams, characterizing the dependence of their expected dynamical behavior on parameters. The framework combines the so-called "coarse time stepper" and arc-length continuation ideas from numerical bifurcation theory with linear dynamic feedback control. An augmented dynamical system is formulated, in which the bifurcation parameter evolution is linked with the microscopic simulation dynamics through feedback laws. The augmentation stably steers the system along both stable and unstable portions of the open-loop bifurcation diagram. The framework is illustrated using kinetic Monte Carlo simulations of simple surface reaction schemes that exhibit both coarse regular turning points and coarse Hopf bifurcations.
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Claussen, M. "Late Quaternary vegetation – climate feedbacks*." Climate of the Past Discussions 5, no. 1 (February 24, 2009): 635–70. http://dx.doi.org/10.5194/cpd-5-635-2009.
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Abstract. Feedbacks between vegetation and other components of the climate system are discussed with respect to their influence on climate dynamics during the late Quaternary, i.e., the last glacial – interglacial cycles. When weighting current understanding based on interpretation of palaeobotanic and palaeoclimatic evidence by numerical climate system models, a number of arguments speak in favour of vegetation dynamics being an amplifier of orbital forcing. (a) The vegetation – snow albedo feedback in synergy with the sea ice – albedo feedback tends to amplify Northern Hemisphere and global mean temperature changes. (b) Variations in the extent of the largest desert on Earth, the Sahara, appear to be amplified by biogeophysical feedback. (c) Biogeochemical feedbacks in the climate system in relation to vegetation migration are supposed to be negative on time scales of glacial cycles. However, with respect to changes in global mean temperature, they are presumably weaker than the positive biogeophysical feedbacks.
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Claussen*, M. "Late Quaternary vegetation-climate feedbacks." Climate of the Past 5, no. 2 (June 3, 2009): 203–16. http://dx.doi.org/10.5194/cp-5-203-2009.
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Abstract. Feedbacks between vegetation and other components of the climate system are discussed with respect to their influence on climate dynamics during the late Quaternary, i.e., the last glacial-interglacial cycles. When weighting current understanding based on interpretation of palaeobotanic and palaeoclimatic evidence by numerical climate system models, a number of arguments speak in favour of vegetation dynamics being an amplifier of orbital forcing. (a) The vegetation-snow albedo feedback in synergy with the sea-ice albedo feedback tends to amplify Northern Hemisphere and global mean temperature changes. (b) Variations in the extent of the largest desert on Earth, the Sahara, appear to be amplified by biogeophysical feedback. (c) Biogeochemical feedbacks in the climate system in relation to vegetation migration are supposed to be negative on time scales of glacial cycles. However, with respect to changes in global mean temperature, they are presumably weaker than the positive biogeophysical feedbacks.
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Deng, Yi, Tae-Won Park, and Ming Cai. "Process-Based Decomposition of the Global Surface Temperature Response to El Niño in Boreal Winter." Journal of the Atmospheric Sciences 69, no. 5 (May 1, 2012): 1706–12. http://dx.doi.org/10.1175/jas-d-12-023.1.
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Abstract This paper reports an attribution analysis that quantifies addible contributions to the observed temperature anomalies from radiative and nonradiative processes in terms of both amplitude and spatial pattern for the two most prominent surface temperature patterns in an El Niño winter. One is the El Niño SST pattern consisting of warming SST anomalies over the eastern equatorial Pacific basin surrounded by cooling SST anomalies in the western and subtropical Pacific, and the other is a tripole surface temperature anomaly characteristic of a positive Pacific–North American (PNA) teleconnection pattern. The decomposition of the observed temperature anomalies is achieved with the coupled atmosphere–surface climate feedback-responses analysis method (CFRAM), which is formulated utilizing energy balance in the atmosphere–surface columns and linearization of radiative energy perturbation. Out of the mean amplitude of 0.78 K of the El Niño SST pattern, the oceanic dynamics and heat storage term alone contributes to 2.34 K. Water vapor feedback adds another 1.6 K whereas both cloud and atmospheric dynamical feedbacks are negative, reducing the mean amplitude by 2.02 and 1.07 K, respectively. Atmospheric dynamical feedback contributes more than 50% (0.73 K) of the mean amplitude (1.32 K) of the PNA surface temperature pattern. Water vapor and surface albedo feedbacks contribute 0.34 and 0.13 K, respectively. The surface processes, including oceanic dynamics in the North Pacific, heat storage anomalies, and surface sensible/latent heat flux anomalies of ocean and land also contribute positively to the PNA surface temperature pattern (about 0.14 K). Cloud and ozone feedback, although very weak, act to oppose the PNA surface temperature anomaly.
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Nguyen, Lan K. "Regulation of oscillation dynamics in biochemical systems with dual negative feedback loops." Journal of The Royal Society Interface 9, no. 73 (March 14, 2012): 1998–2010. http://dx.doi.org/10.1098/rsif.2012.0028.
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Feedback controls are central to cellular regulation. Negative-feedback mechanisms are well known to underline oscillatory dynamics. However, the presence of multiple negative-feedback mechanisms is common in oscillatory cellular systems, raising intriguing questions of how they cooperate to regulate oscillations. In this work, we studied the dynamical properties of a set of general biochemical motifs with dual, nested negative-feedback structures. We showed analytically and then confirmed numerically that, in these motifs, each negative-feedback loop exhibits distinctly different oscillation-controlling functions. The longer, outer feedback loop was found to promote oscillations, whereas the short, inner loop suppresses and can even eliminate oscillations. We found that the position of the inner loop within the coupled motifs affects its repression strength towards oscillatory dynamics. Bifurcation analysis indicated that emergence of oscillations may be a strict parametric requirement and thus evolutionarily tricky. Investigation of the quantitative features of oscillations (i.e. frequency, amplitude and mean value) revealed that coupling negative feedback provides robust tuning of the oscillation dynamics. Finally, we demonstrated that the mitogen-activated protein kinase (MAPK) cascades also display properties seen in the general nested feedback motifs. The findings and implications in this study provide novel understanding of biochemical negative-feedback regulation in a mixed wiring context.
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Ng, Benjamin, Wenju Cai, and Kevin Walsh. "Nonlinear Feedbacks Associated with the Indian Ocean Dipole and Their Response to Global Warming in the GFDL-ESM2M Coupled Climate Model." Journal of Climate 27, no. 11 (May 29, 2014): 3904–19. http://dx.doi.org/10.1175/jcli-d-13-00527.1.
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Abstract A feature of the Indian Ocean dipole (IOD) is its positive skewness, with cold IOD east pole (IODE) sea surface temperature anomalies (SSTAs) exhibiting larger amplitudes than warm SSTAs. Using the coupled Geophysical Fluid Dynamics Laboratory Earth System Model with Modular Ocean Model version 4 (MOM4) component (GFDL-ESM2M), the role of nonlinear feedbacks in generating this positive skewness is investigated and their response to global warming examined. These feedbacks are a nonlinear dynamic heating process, the Bjerknes feedback, wind–evaporation–SST feedback, and SST–cloud–radiation feedback. Nonlinear dynamic heating assists IOD skewness by strongly damping warm IODE SSTAs and reinforcing cold IODE anomalies. In a warmer climate, the damping strengthens while the reinforcement weakens. The SST–thermocline relationship is part of the positive Bjerknes feedback and contributes strongly to IOD skewness as it is weak during the development of warm IODE SSTAs, but strong during the development of cold IODE SSTAs. In response to global warming, this relationship displays weaker asymmetry associated with weaker westerly winds over the central equatorial Indian Ocean. The negative SST–cloud–radiation feedback is also asymmetric with cold IODE SSTAs less damped by incoming shortwave radiation. Under global warming, the damping of cold IODE SSTAs shows little change but warm IODE SSTAs become more damped. This stronger damping is a symptom of negative IODs becoming stronger in amplitude due to the mean IODE thermocline shoaling. The wind–evaporation–SST feedback does not contribute to IOD asymmetry with cold IODE SSTAs decreasing evaporation, which in turn warms the surface. However, as this study focuses on one model, the response of these feedbacks to global warming is uncertain.
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Li, Lijuan, Bin Wang, and Guang J. Zhang. "The Role of Moist Processes in Shortwave Radiative Feedback during ENSO in the CMIP5 Models." Journal of Climate 28, no. 24 (December 15, 2015): 9892–908. http://dx.doi.org/10.1175/jcli-d-15-0276.1.
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Abstract The weak negative shortwave (SW) radiative feedback αsw during El Niño–Southern Oscillation (ENSO) over the equatorial Pacific is a common problem in the models participating in phase 5 of the Coupled Model Intercomparison Project (CMIP5). In this study, the causes for the αsw biases are analyzed using three-dimensional cloud fraction and liquid water path (LWP) provided by the 17 CMIP5 models and the relative roles of convective and stratiform rainfall feedbacks in αsw are explored. Results show that the underestimate of SW feedback is primarily associated with too negative cloud fraction and LWP feedbacks in the boundary layers, together with insufficient middle and/or high cloud and dynamics feedbacks, in both the CMIP and Atmospheric Model Intercomparsion Project (AMIP) runs, the latter being somewhat better. The underestimations of SW feedbacks are due to both weak negative SW responses to El Niño, especially in the CMIP runs, and strong positive SW responses to La Niña, consistent with their biases in cloud fraction, LWP, and dynamics responses to El Niño and La Niña. The convective rainfall feedback, which is largely reduced owing to the excessive cold tongue in the CMIP runs compared with their AMIP counterparts, contributes more to the difference of SW feedback (mainly under El Niño conditions) between the CMIP and AMIP runs, while the stratiform rainfall plays a more important role in SW feedback during La Niña.
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CHEN, GUANRONG, JIALIANG LU, BRENT NICHOLAS, and SWATIPRAKASH M. RANGANATHAN. "BIFURCATION DYNAMICS IN CONTROL SYSTEMS." International Journal of Bifurcation and Chaos 09, no. 01 (January 1999): 287–93. http://dx.doi.org/10.1142/s021812749900016x.
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This paper is to report the observation that when the popular time-delayed feedback strategy is used for control purpose, it may actually create unwanted bifurcations. Hopf bifurcation created by delayed feedback control is the main concern of this article, but some other types of bifurcations are also observed to exist in such delayed-feedback control systems. The observations are illustrated by computer simulations.
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Liu, Fei, and Bin Wang. "Roles of the Moisture and Wave Feedbacks in Shaping the Madden–Julian Oscillation." Journal of Climate 30, no. 24 (December 2017): 10275–91. http://dx.doi.org/10.1175/jcli-d-17-0003.1.
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This study investigates the moisture and wave feedbacks in the Madden–Julian oscillation (MJO) dynamics by applying the general three-way interaction theoretical model. The three-way interaction model can reproduce observed large-scale characteristics of the MJO in terms of horizontal quadrupole-vortex structure, vertically tilted structure led by planetary boundary layer (PBL) convergence, slow eastward propagation with a period of 30–90 days, and planetary-scale circulation. The moisture feedback effects can be identified in this model by using diagnostic thermodynamic and momentum equations, and the wave feedback effects are investigated by using a diagnostic moisture equation. The moisture feedback is found to be responsible for producing the MJO dispersive modes when the convective adjustment process is slow. The moisture feedback mainly acts to reduce the frequency and growth rate of the short waves, while leaving the planetary waves less affected, so neglecting the moisture feedback is a good approximation for the wavenumber-1 MJO. The wave feedback is shown to slow down the eastward propagation and increase the growth rate of the planetary waves. The wave feedback becomes weak when the convective adjustment time increases, so neglecting the wave feedback is a good approximation for the MJO dynamics during a slow adjustment process. Sensitivities of these two feedbacks to other parameters are also discussed. These theoretical findings suggest that the two feedback processes, and thus the behaviors of the simulated MJO mode, should be sensitive to the parameters used in cumulus parameterizations.
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Hongray, Thotreithem, and Janaki Balakrishnan. "Dynamics of bow-tie shaped bursting: Forced pendulum with dynamic feedback." Chaos: An Interdisciplinary Journal of Nonlinear Science 26, no. 12 (December 2016): 123107. http://dx.doi.org/10.1063/1.4971411.
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Jarvis, A. "The magnitudes and timescales of global mean surface temperature feedbacks in climate models." Earth System Dynamics 2, no. 2 (December 15, 2011): 213–21. http://dx.doi.org/10.5194/esd-2-213-2011.
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Abstract. Because of the fundamental role feedbacks play in determining the response of surface temperature to perturbations in radiative forcing, it is important we understand the dynamic characteristics of these feedbacks. Rather than attribute the aggregate surface temperature feedback to particular physical processes, this paper adopts a linear systems approach to investigate the partitioning with respect to the timescale of the feedbacks regulating global mean surface temperature in climate models. The analysis reveals that there is a dominant net negative feedback realised on an annual timescale and that this is partially attenuated by a spectrum of positive feedbacks with characteristic timescales in the range 10 to 1000 yr. This attenuation was composed of two discrete phases which are attributed to the equilibration of "diffusive – mixed layer" and "circulatory – deep ocean" ocean heat uptake. The diffusive equilibration was associated with time constants on the decadal timescale and accounted for approximately 75 to 80 percent of the overall ocean heat feedback, whilst the circulatory equilibration operated on a centennial timescale and accounted for the remaining 20 to 25 percent of the response. This suggests that the dynamics of the transient ocean heat uptake feedback first discussed by Baker and Roe (2009) tends to be dominated by loss of diffusive heat uptake in climate models, rather than circulatory deep ocean heat equilibration.
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Tran, Thanh T., and Oscar R. Gonzalez. "Backstepping-based control methodology for aircraft roll dynamics." Proceedings of the Institution of Mechanical Engineers, Part I: Journal of Systems and Control Engineering 234, no. 4 (July 3, 2019): 566–74. http://dx.doi.org/10.1177/0959651819860294.
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This article investigates a backstepping-based control method for aircraft roll dynamics. The research starts with a formulation of backstepping control law for a general class of a strict-feedback form of nonlinear dynamic systems. The backstepping control law is formulated by introducing a normal tracking error. Then, control and virtual control inputs are selected by addressing each layer of the design process with a chosen corresponding control Lyapunov function. The parameter assignment in each design layer is selected to ensure the stability of the entire system. Next, a backstepping-based control algorithm with online-gain schedule or variable gains is provided for the standard strict-feedback system. In order to validate the proposed method, application of roll dynamics of aircraft is implemented. Dynamic equations of free-to-roll aircraft model is restructured in a standard strict-feedback model for formulating the backstepping control. Then, a backstepping control–based control strategy is provided for aircraft free-to-roll dynamics. Indoor experimental and simulation studies of roll angle control for the L-59 free-to-roll aircraft model at NASA Langley Research Center are implemented to verify and validate the proposed approach.
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Huang, Rongsheng, and Jinzhi Lei. "Dynamics of gene expression with positive feedback to histone modifications at bivalent domains." International Journal of Modern Physics B 32, no. 07 (March 5, 2018): 1850075. http://dx.doi.org/10.1142/s0217979218500753.
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Experiments have shown that in embryonic stem cells, the promoters of many lineage-control genes contain “bivalent domains”, within which the nucleosomes possess both active (H3K4me3) and repressive (H3K27me3) marks. Such bivalent modifications play important roles in maintaining pluripotency in embryonic stem cells. Here, to investigate gene expression dynamics when there are regulations in bivalent histone modifications and random partition in cell divisions, we study how positive feedback to histone methylation/demethylation controls the transition dynamics of the histone modification patterns along with cell cycles. We constructed a computational model that includes dynamics of histone marks, three-stage chromatin state transitions, transcription and translation, feedbacks from protein product to enzymes to regulate the addition and removal of histone marks, and the inheritance of nucleosome state between cell cycles. The model reveals how dynamics of both nucleosome state transition and gene expression are dependent on the enzyme activities and feedback regulations. Results show that the combination of stochastic histone modification at each cell division and the deterministic feedback regulation work together to adjust the dynamics of chromatin state transition in stem cell regenerations.
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Liu, Zhengyu, Na Wen, and Yun Liu. "On the Assessment of Nonlocal Climate Feedback. Part I: The Generalized Equilibrium Feedback Assessment*." Journal of Climate 21, no. 1 (January 1, 2008): 134–48. http://dx.doi.org/10.1175/2007jcli1826.1.
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Abstract A statistical method is developed to assess the full climate feedback of nonlocal climate feedbacks. The method is a multivariate generalization of the univariate equilibrium feedback assessment (EFA) method of Frankignoul et al. As a pilot study here, the generalized EFA (GEFA) is applied to the assessment of the feedback response of sea surface temperature (SST) on surface heat flux in a simple ocean–atmosphere model that includes atmospheric advection. It is shown that GEFA can capture major features of nonlocal climate feedback and sheds light on the dynamics of the atmospheric response, as long as the spatial resolution (or spatial degree of freedom) is not very high. Given a sample size, sampling error tends to increase significantly with the spatial resolution of the data. As a result, useful estimates of the feedback can only be obtained at sufficiently low resolution. The sampling error is also found to increase significantly with the spatial scale of the atmospheric forcing and, in turn, the SST variability. This implies the potential difficulty in distinguishing the nonlocal feedbacks arising from small-scale SST variability. These deficiencies call for further improvements on the assessment methods for nonlocal climate feedbacks.
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Zhang, W., C. Jansson, P. A. Miller, B. Smith, and P. Samuelsson. "Biogeophysical feedbacks enhance Arctic terrestrial carbon sink in regional Earth system dynamics." Biogeosciences Discussions 11, no. 5 (May 12, 2014): 6715–54. http://dx.doi.org/10.5194/bgd-11-6715-2014.
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Abstract. Continued warming of the Arctic will likely accelerate terrestrial carbon (C) cycling by increasing both uptake and release of C. There are still large uncertainties in modelling Arctic terrestrial ecosystems as a source or sink of C. Most modelling studies assessing or projecting the future fate of C exchange with the atmosphere are based an either stand-alone process-based models or coupled climate–C cycle general circulation models, in either case disregarding biogeophysical feedbacks of land surface changes to the atmosphere. To understand how biogeophysical feedbacks will impact on both climate and C budget over Arctic terrestrial ecosystems, we apply the regional Earth system model RCA-GUESS over the CORDEX-Arctic domain. The model is forced with lateral boundary conditions from an GCMs CMIP5 climate projection under the RCP 8.5 scenario. We perform two simulations with or without interactive vegetation dynamics respectively to assess the impacts of biogeophysical feedbacks. Both simulations indicate that Arctic terrestrial ecosystems will continue to sequester C with an increased uptake rate until 2060s–2070s, after which the C budget will return to a weak C sink as increased soil respiration and biomass burning outpaces increased net primary productivity. The additional C sinks arising from biogeophysical feedbacks are considerable, around 8.5 Gt C, accounting for 22% of the total C sinks, of which 83.5% are located in areas of Arctic tundra. Two opposing feedback mechanisms, mediated by albedo and evapotranspiration changes respectively, contribute to this response. Albedo feedback dominates over winter and spring season, amplifying the near-surface warming by up to 1.35 K in spring, while evapotranspiration feedback dominates over summer exerting the evaporative cooling by up to 0.81 K. Such feedbacks stimulate vegetation growth with an earlier onset of growing-season, leading to compositional changes in woody plants and vegetation redistribution.
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Willeit, M., A. Ganopolski, and G. Feulner. "Asymmetry and uncertainties in biogeophysical climate–vegetation feedback over a range of CO<sub>2</sub> forcings." Biogeosciences 11, no. 1 (January 3, 2014): 17–32. http://dx.doi.org/10.5194/bg-11-17-2014.
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Abstract. Climate–vegetation feedback has the potential to significantly contribute to climate change, but little is known about its range of uncertainties. Here, using an Earth system model of intermediate complexity we address possible uncertainties in the strength of the biogeophysical climate–vegetation feedback using a single-model multi-physics ensemble. Equilibrium experiments with halving (140 ppm) and doubling (560 ppm) of CO2 give a contribution of the vegetation–climate feedback to global temperature change in the range −0.3 to −0.1 °C and −0.1 to 0.2 °C, respectively. There is an asymmetry between warming and cooling, with a larger, positive vegetation–climate feedback in the lower CO2 climate. Hotspots of climate–vegetation feedback are the boreal zone, the Amazon rainforest and the Sahara. Albedo parameterization is the dominant source of uncertainty in the subtropics and at high northern latitudes, while uncertainties in evapotranspiration are more relevant in the tropics. We analyse the separate impact of changes in stomatal conductance, leaf area index and vegetation dynamics on climate and we find that different processes are dominant in lower and higher CO2 worlds. The reduction in stomatal conductance gives the main contribution to temperature increase for a doubling of CO2, while dynamic vegetation is the dominant process in the CO2 halving experiments. Globally the climate–vegetation feedback is rather small compared to the sum of the fast climate feedbacks. However, it is comparable to the amplitude of the fast feedbacks at high northern latitudes where it can contribute considerably to polar amplification. The uncertainties in the climate–vegetation feedback are comparable to the multi-model spread of the fast climate feedbacks.
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Lloyd, James, Eric Guilyardi, and Hilary Weller. "The Role of Atmosphere Feedbacks during ENSO in the CMIP3 Models. Part III: The Shortwave Flux Feedback." Journal of Climate 25, no. 12 (June 15, 2012): 4275–93. http://dx.doi.org/10.1175/jcli-d-11-00178.1.
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Abstract Previous studies using coupled general circulation models (GCMs) suggest that the atmosphere model plays a dominant role in the modeled El Niño–Southern Oscillation (ENSO), and that intermodel differences in the thermodynamical damping of sea surface temperatures (SSTs) are a dominant contributor to the ENSO amplitude diversity. This study presents a detailed analysis of the shortwave flux feedback (αSW) in 12 Coupled Model Intercomparison Project phase 3 (CMIP3) simulations, motivated by findings that αSW is the primary contributor to model thermodynamical damping errors. A “feedback decomposition method,” developed to elucidate the αSW biases, shows that all models underestimate the dynamical atmospheric response to SSTs in the eastern equatorial Pacific, leading to underestimated αSW values. Biases in the cloud response to dynamics and the shortwave interception by clouds also contribute to errors in αSW. Changes in the αSW feedback between the coupled and corresponding atmosphere-only simulations are related to changes in the mean dynamics. A large nonlinearity is found in the observed and modeled SW flux feedback, hidden when linearly calculating αSW. In the observations, two physical mechanisms are proposed to explain this nonlinearity: 1) a weaker subsidence response to cold SST anomalies than the ascent response to warm SST anomalies and 2) a nonlinear high-level cloud cover response to SST. The shortwave flux feedback nonlinearity tends to be underestimated by the models, linked to an underestimated nonlinearity in the dynamical response to SST. The process-based methodology presented in this study may help to correct model ENSO atmospheric biases, ultimately leading to an improved simulation of ENSO in GCMs.
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Chawla, Nitya, Allison S. Gabriel, Jason J. Dahling, and Kajal Patel. "Feedback Dynamics Are Critical to Improving Performance Management Systems." Industrial and Organizational Psychology 9, no. 2 (June 2016): 260–66. http://dx.doi.org/10.1017/iop.2016.8.
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Colquitt, Murphy, and Ollander-Krane (Adler et al., 2016) argue that performance ratings are problematic in part because of the problems associated with feedback: Ratees dislike and dismiss performance feedback, raters are reluctant to provide tough feedback, and organizations do not enact research findings about improving feedback processes (Adler et al.). Discarding performance ratings on these grounds is effectively “throwing out the baby with the bath water,” given that we know quite a lot about how to improve the delivery and receptivity of feedback. Our commentary is intended to briefly illustrate ways to leverage research on feedback receptivity to improve performance management systems. Specifically, we focus on (a) cultivating supportive feedback environments, (b) integrating employee coaching into performance management systems, and (c) attending to the characteristics of feedback recipients to understand how they process feedback.
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Barreiro, A., and J. Aracil. "Stability of Feedback Systems with Uncertain Dynamics." IFAC Proceedings Volumes 25, no. 10 (June 1992): 127–32. http://dx.doi.org/10.1016/s1474-6670(17)50810-1.
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Barreiro, A., and J. Aracil. "Stability of feedback systems with uncertain dynamics." Annual Review in Automatic Programming 17 (January 1992): 127–32. http://dx.doi.org/10.1016/s0066-4138(09)91022-9.
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