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1
Omel’chenko, Oleh E., and Tamás Tél. "Focusing on transient chaos." Journal of Physics: Complexity 3, no. 1 (March 1, 2022): 010201. http://dx.doi.org/10.1088/2632-072x/ac5566.
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Abstract Recent advances in the field of complex, transiently chaotic dynamics are reviewed, based on the results published in the focus issue of J. Phys. Complex. on this topic. One group of achievements concerns network dynamics where transient features are intimately related to the degree and stability of synchronization, as well as to the network topology. A plethora of various applications of transient chaos are described, ranging from the collective motion of active particles, through the operation of power grids, cardiac arrhythmias, and magnetohydrodynamical dynamos, to the use of machine learning to predict time evolutions. Nontraditional forms of transient chaos are also explored, such as the temporal change of the chaoticity in the transients (called doubly transient chaos), as well as transients in systems subjected to parameter drift, the paradigm of which is climate change.
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Hastings, Alan, Karen C. Abbott, Kim Cuddington, Tessa Francis, Gabriel Gellner, Ying-Cheng Lai, Andrew Morozov, Sergei Petrovskii, Katherine Scranton, and Mary Lou Zeeman. "Transient phenomena in ecology." Science 361, no. 6406 (September 6, 2018): eaat6412. http://dx.doi.org/10.1126/science.aat6412.
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The importance of transient dynamics in ecological systems and in the models that describe them has become increasingly recognized. However, previous work has typically treated each instance of these dynamics separately. We review both empirical examples and model systems, and outline a classification of transient dynamics based on ideas and concepts from dynamical systems theory. This classification provides ways to understand the likelihood of transients for particular systems, and to guide investigations to determine the timing of sudden switches in dynamics and other characteristics of transients. Implications for both management and underlying ecological theories emerge.
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Hastings, Alan, Karen C. Abbott, Kim Cuddington, Tessa B. Francis, Ying-Cheng Lai, Andrew Morozov, Sergei Petrovskii, and Mary Lou Zeeman. "Effects of stochasticity on the length and behaviour of ecological transients." Journal of The Royal Society Interface 18, no. 180 (July 2021): 20210257. http://dx.doi.org/10.1098/rsif.2021.0257.
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There is a growing recognition that ecological systems can spend extended periods of time far away from an asymptotic state, and that ecological understanding will therefore require a deeper appreciation for how long ecological transients arise. Recent work has defined classes of deterministic mechanisms that can lead to long transients. Given the ubiquity of stochasticity in ecological systems, a similar systematic treatment of transients that includes the influence of stochasticity is important. Stochasticity can of course promote the appearance of transient dynamics by preventing systems from settling permanently near their asymptotic state, but stochasticity also interacts with deterministic features to create qualitatively new dynamics. As such, stochasticity may shorten, extend or fundamentally change a system’s transient dynamics. Here, we describe a general framework that is developing for understanding the range of possible outcomes when random processes impact the dynamics of ecological systems over realistic time scales. We emphasize that we can understand the ways in which stochasticity can either extend or reduce the lifetime of transients by studying the interactions between the stochastic and deterministic processes present, and we summarize both the current state of knowledge and avenues for future advances.
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Friston, Karl J. "The labile brain. I. Neuronal transients and nonlinear coupling." Philosophical Transactions of the Royal Society of London. Series B: Biological Sciences 355, no. 1394 (February 29, 2000): 215–36. http://dx.doi.org/10.1098/rstb.2000.0560.
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In this, the first of three papers, the nature of, and motivation for, neuronal transients is described in relation to characterizing brain dynamics. This paper deals with some basic aspects of neuronal dynamics, interactions, coupling and implicit neuronal codes. The second paper develops neuronal transients and nonlinear coupling in the context of dynamic instability and complexity, and suggests that instability or lability is necessary for adaptive self–organization. The final paper addresses the role of neuronal transients through information theory and the emergence of spatio–temporal receptive fields and functional specialization. By considering the brain as an ensemble of connected dynamic systems one can show that a sufficient description of neuronal dynamics comprises neuronal activity at a particular time and its recent history. This history constitutes a neuronal transient. As such, transients represent a fundamental metric of neuronal interactions and, implicitly, a code employed in the functional integration of brain systems. The nature of transients, expressed conjointly in distinct neuronal populations, reflects the underlying coupling among populations. This coupling may be synchronous (and possibly oscillatory) or asynchronous. A critical distinction between synchronous and asynchronous coupling is that the former is essentially linear and the latter is nonlinear. The nonlinear nature of asynchronous coupling enables the rich, context–sensitive interactions that characterize real brain dynamics, suggesting that it plays a role in functional integration that may be as important as synchronous interactions. The distinction between linear and nonlinear coupling has fundamental implications for the analysis and characterization of neuronal interactions, most of which are predicated on linear (synchronous) coupling (e.g. crosscorrelograms and coherence). Using neuromagnetic data it is shown that nonlinear (asynchronous) coupling is, in fact, more abundant and can be more significant than synchronous coupling.
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Paar, V., N. Pavin, N. Paar, and B. Novaković. "Nonlinear dynamics of a single-degree robot model Part 2: Onset of chaotic transients." Robotica 18, no. 2 (March 2000): 201–8. http://dx.doi.org/10.1017/s0263574799001952.
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In Part 1 of this paper we have investigated numerically the quasiperiodic and frequency locked solutions of mathematical model of a robot with one degree of freedom. In this paper we extend our investigations to the region of transient chaos. The zones of chaotic transients are very broad and lie beyond the parameter range of engineering significance. Transiently chaotic zones exhibit a complex structure, fractally intertwined with tongues of regular pattern and cover a broad range of control parameter L. The crisis point for the onset of sustained chaos lies extremely far from the point of onset of transient chaos.
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Zhao, H., F. K. Choy, and M. J. Braun. "Transient and Steady State Vibration Analysis of a Wavy Thrust Bearing." Journal of Tribology 128, no. 1 (June 22, 2005): 139–45. http://dx.doi.org/10.1115/1.2033900.
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This paper describes a numerical procedure for analyzing the dynamics of transient and steady state vibrations in a wavy thrust bearing. The major effects of the wavy geometry and the operating parameters on the dynamic characteristics of the bearing had been discussed in a previous paper; the present paper thus concentrates on examining the relationships between the development of the transient and steady state vibrations when operating conditions are parametrically varied. Special attention is given to the development of steady state vibrations from initial transients with comparisons and consequences to the overall system stability. Numerical based vibration signature analysis procedures are then used to identify and quantify the transient vibrations. The conclusions provide general indicators for designing wavy thrust bearings that are less susceptible to transients induced by external perturbations.
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Granzier, H. L., A. Mattiazzi, and G. H. Pollack. "Sarcomere dynamics during isotonic velocity transients in single frog muscle fibers." American Journal of Physiology-Cell Physiology 259, no. 2 (August 1, 1990): C266—C278. http://dx.doi.org/10.1152/ajpcell.1990.259.2.c266.
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If the load on a tetanized fiber is abruptly changed to a new steady value, the ensuing fiber length change shows the well-known "isotonic velocity transient," in which the velocity oscillates before settling at some steady value. We studied sarcomere dynamics during these transients using two methods: optical diffraction and a segment-length method. Our principal aim was to determine whether these transients might be a reflection of the fact that sarcomere shortening is often found to be stepwise. We found that pauses in sarcomere shortening occurred during the low-velocity phases of the transient and that steps of sarcomere shortening occurred during the high-velocity phases. Thus the isotonic transient appears to arise from the steps. In addition to the isotonic transient, we studied the well-known isometric transient, in which fiber length is abruptly changed, and ensuing tension response is measured. Again, we found that the transient may be a reflection of the stepwise shortening pattern.
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Toroptsev, E. L., A. S. Marakhovskii, and R. R. Duszynski. "Intersectoral modeling of transients." Economic Analysis: Theory and Practice 19, no. 3 (March 30, 2020): 564–85. http://dx.doi.org/10.24891/ea.19.3.564.
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Subject. The article considers structural transition processes in macroeconomics. Objectives. The aim is to present our own concept and mathematical tools to study structural transitions in macroeconomics. Dynamic inter-industry balance enables to formalize the problem in the form of a Koshi task for ordinary differential equations. Methods. The methodology components include the basics of inter-industry and numerical analysis and modeling of linear or linearized dynamic systems, integral criteria of system dynamics, stability and quality of transitional processes. We also apply a technique for analyzing the own dynamic properties of economic systems that solve the same sustainability-related challenges, but on the basis of algebraic methods and criteria. Results. We offer methods and mathematical tools for numerical study of sustainability and structural dynamics of macroeconomics. These methods are focused on integrating high-dimensional balance models and integral criteria for the quality of transition periods in the economy. The paper unveils advantages of calculating the matrix exponential and its integral in tasks involving analysis and forecasting, over other numerical methods. The proposed method permits to effectively build a difference scheme to integrate with any step of observation of the solution. In this case, the work step of integration is generated in the algorithm automatically, depending on changes in gross output. Conclusions. The paper presents a unique option to analyze transitional processes in macroeconomics. It is designed to develop and evaluate the results of pursued economic policy.
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Friston, Karl J. "Transients, Metastability, and Neuronal Dynamics." NeuroImage 5, no. 2 (February 1997): 164–71. http://dx.doi.org/10.1006/nimg.1997.0259.
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Dudkowski, Dawid, Patrycja Jaros, and Tomasz Kapitaniak. "Extreme transient dynamics." Chaos: An Interdisciplinary Journal of Nonlinear Science 32, no. 12 (December 2022): 121101. http://dx.doi.org/10.1063/5.0131768.
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We study the extreme transient dynamics of four self-excited pendula coupled via the movable beam. A slight difference in the pendula lengths induces the appearance of traveling phase behavior, within which the oscillators synchronize, but the phases between the nodes change in time. We discuss various scenarios of traveling states (involving different pendula) and their properties, comparing them with classical synchronization patterns of phase-locking. The research investigates the problem of transient dynamics preceding the stabilization of the network on a final synchronous attractor, showing that the width of transient windows can become extremely long. The relation between the behavior of the system within the transient regime and its initial conditions is examined and described. Our results include both identical and non-identical pendula masses, showing that the distribution of the latter ones is related to the transients. The research performed in this paper underlines possible transient problems occurring during the analysis of the systems when the slow evolution of the dynamics can be misinterpreted as the final behavior.
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Feller, M. B., K. R. Delaney, and D. W. Tank. "Presynaptic calcium dynamics at the frog retinotectal synapse." Journal of Neurophysiology 76, no. 1 (July 1, 1996): 381–400. http://dx.doi.org/10.1152/jn.1996.76.1.381.
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1. We characterized the kinetics of presynaptic Ca2+ ion concentration in optic nerve fibers and terminals of the optic tectum in Rana pipiens with the use of microfluorimetry. Isolated frog brains were incubated with the membrane-permeant tetraacetoxymethyl ester (AM) of the Ca2+ indicator fura-2. An optic nerve shock caused a transient decrease in the 380-nm excited fluorescence in the optic tectum with a rise time of <15 ms and a recovery to prestimulus levels on a time scale of seconds. 2. In normal saline, the amplitude of the fluorescence transients was dependent on stimulus intensity and at all levels it was directly correlated with the amplitude of postsynaptic field potentials produced by activation of unmyelinated optic nerve fibers. In the presence of the non-N-methyl-D-aspartate glutamate receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione, the amplitude and time course of fluorescence transients remained essentially unchanged while postsynaptic field potential amplitude was greatly reduced. Replacing extracellular Ca2+ with Ba2+ blocked unfacilitated postsynaptic field potentials while fluorescence transients remained significant. In reduced-Ca2+ salines (<1 mM), the amplitude of fluorescence transients increased approximately linearly with extracellular [Ca2+], whereas the amplitude the corresponding field potential was nonlinearly related to the fluorescent transient amplitude (approximately 2.5 power). In thin sections of labeled tecta, fluorescence labeling was localized to 1-micron puncta in the termination zone of optic nerve fibers in the superficial layers. Taken together, these results provide strong evidence that the fluorescence transients correspond to an increase in Ca2+ in presynaptic terminals of unmyelinated optic nerve fibers. 3. During trains of optic nerve stimulation, the amplitude of fluorescence transients to succeeding action potentials became smaller. The decrement of the amplitudes was not observed in mag-fura-5-labeled tecta, when the intracellular Ca2+ buffering capacity of fura-2-labeled terminals was increased by incubation with bis-(o-aminophenoxy)-N,N,N',N'-tetraacetic acid (BAPTA)-AM or ethylene glycol-bis (beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA)-AM, or in low-Ca2+ saline. We conclude that the Ca2+ influx per action potential is constant during the train and that the reduced response was produced by saturation of the fura-2. We provide a mathematical analysis of this saturation effect and use it to estimate the Ca2+ change per action potential. 4. Both BAPTA-AM and EGTA-AM reduced the overall amplitude of fura-2-measured Ca2+ transients and reduced the saturation effect in action potential trains. However, there was a qualitative difference in their effects on the shape of the transient. Incubation with the fast buffer BAPTA prolonged the decay to baseline. In contrast, the slow buffer EGTA (or EDTA) produced an initial decay faster than the control condition while also producing the slower subsequent phase observed with BAPTA. We demonstrate that these results are consistent with numerical simulations of Ca2+ dynamics in a single-compartment model where the fast initial decay is produced by the forward rate of Ca2+ binding to EGTA. 5. Ca2+ influx into tectal presynaptic structures, and also into unmyelinated axons in the isolated optic nerve, was diminished (60-70%) in the presence of the voltage-activated Ca2+ channel blocker omega-conotoxin GVIA, but was only weakly affected (approximately 10%) by omega-agatoxin IVA. 6. After 10- to 50-Hz stimulus trains, synaptic enhancement of unmyelinated fibers decayed with a characteristic time similar to fura-2 fluorescence decays. Incubation with EDTA-AM or EGTA-AM produced little effect on evoked release but reduced both the amplitude of the fura-2-measured Ca2+ transient and the amplitude of short-term synaptic enhancement.
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López Alarcón, María Micaela, Ainhoa Rodríguez de Yurre, Juan Ignacio Felice, Emiliano Medei, and Ariel L. Escobar. "Phase 1 repolarization rate defines Ca2+ dynamics and contractility on intact mouse hearts." Journal of General Physiology 151, no. 6 (April 18, 2019): 771–85. http://dx.doi.org/10.1085/jgp.201812269.
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In the heart, Ca2+ influx through L-type Ca2+ channels triggers Ca2+ release from the sarcoplasmic reticulum. In most mammals, this influx occurs during the ventricular action potential (AP) plateau phase 2. However, in murine models, the influx through L-type Ca2+ channels happens in early repolarizing phase 1. The aim of this work is to assess if changes in the open probability of 4-aminopyridine (4-AP)–sensitive Kv channels defining the outward K+ current during phase 1 can modulate Ca2+ currents, Ca2+ transients, and systolic pressure during the cardiac cycle in intact perfused beating hearts. Pulsed local-field fluorescence microscopy and loose-patch photolysis were used to test the hypothesis that a decrease in a transient K+ current (Ito) will enhance Ca2+ influx and promote a larger Ca2+ transient. Simultaneous recordings of Ca2+ transients and APs by pulsed local-field fluorescence microscopy and loose-patch photolysis showed that a reduction in the phase 1 repolarization rate increases the amplitude of Ca2+ transients due to an increase in Ca2+ influx through L-type Ca2+ channels. Moreover, 4-AP induced an increase in the time required for AP to reach 30% repolarization, and the amplitude of Ca2+ transients was larger in epicardium than endocardium. On the other hand, the activation of Ito with NS5806 resulted in a reduction of Ca2+ current amplitude that led to a reduction of the amplitude of Ca2+ transients. Finally, the 4-AP effect on AP phase 1 was significantly smaller when the L-type Ca2+ current was partially blocked with nifedipine, indicating that the phase 1 rate of repolarization is defined by the competition between an outward K+ current and an inward Ca2+ current.
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Miles, David M., Andrew D. Howarth, and Greg A. Enno. "In situ calibration of offsetting magnetometer feedback transients on the Cassiope spacecraft." Geoscientific Instrumentation, Methods and Data Systems 8, no. 2 (August 13, 2019): 187–95. http://dx.doi.org/10.5194/gi-8-187-2019.
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Abstract. We present an in situ calibration process to derive the transient behavior of the offsetting fluxgate magnetometer (MGF) instruments on the Cassiope spacecraft. The dynamic behavior of the MGF changed on orbit following a software update. Characterizing the new instrument dynamics during normal spacecraft operations and then removing the transients was confounded by significant magnetic interference from the reaction wheels used to orient the spacecraft. Special operations were performed where data were taken in a safehold mode, with the reaction wheels stopped, following a single-event upset of the spacecraft bus flight computer after transiting the South Atlantic Anomaly. The slow single-axis rotation of the safehold mode was used to characterize the fluxgate's new feedback dynamics. This characterization process was then adapted for routine operation intervals with slow reaction wheel rates to allow the transient behavior to be characterized over long intervals of data spanning a wide range of temperatures. Subtracting these characterized transients from the flight data improves the instrument's noise floor and allows the instrument to accurately track rapidly changing local fields without loss of measurement fidelity. More generally, this characterization process should apply to other situations where the dynamics of an offsetting instrument must be calibrated in situ.
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MUEZZINOGLU, MEHMET K., IRMA TRISTAN, RAMON HUERTA, VALENTIN S. AFRAIMOVICH, and MIKHAIL I. RABINOVICH. "TRANSIENTS VERSUS ATTRACTORS IN COMPLEX NETWORKS." International Journal of Bifurcation and Chaos 20, no. 06 (June 2010): 1653–75. http://dx.doi.org/10.1142/s0218127410026745.
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Understanding and predicting the behavior of complex multiagent systems like brain or ecological food net requires new approaches and paradigms. Traditional analyses based on just asymptotic results of behavior as time goes to infinity, or on straightforward mathematical images that can accommodate only fixed points or limit cycles do not tell much about these systems. To obtain sensible dynamical models of natural phenomena, such as the reproducible order observed in ecological, cognitive or behavioral experiments, one cannot afford to neglect the transient dynamics of the underlying complex network. In disclosing such dynamical mechanisms, the focus of interest must be on reproducible or, even, structurally stable transients. In this tutorial, we formulate the Winnerless Competition (WLC) principle that induces robust transient dynamics in open complex networks. The main point of WLC principle is the transformation of the acquired information into ensemble (spatio)-temporal output via intrinsic transient dynamics of the network. Such encoding provides a reproducible transient response, whose geometrical image in phase space is a stable heteroclinic sequence. We compile a diverse list of natural phenomena which can be rigorously modeled by the WLC. Together with the experimental and numerical results of the networks with different levels of complexity, we evaluate the robustness and reproducibility of the WLC dynamics and discuss the advantages of future possible application of the discussed approach.
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Koester, Helmut J., and Bert Sakmann. "Calcium dynamics in single spines during coincident pre- and postsynaptic activity depend on relative timing of back-propagating action potentials and subthreshold excitatory postsynaptic potentials." Proceedings of the National Academy of Sciences 95, no. 16 (August 4, 1998): 9596–601. http://dx.doi.org/10.1073/pnas.95.16.9596.
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We compared the transient increase of Ca2+ in single spines on basal dendrites of rat neocortical layer 5 pyramidal neurons evoked by subthreshold excitatory postsynaptic potentials (EPSPs) and back-propagating action potentials (APs) by using calcium fluorescence imaging. AP-evoked Ca2+ transients were detected in both the spines and in the adjacent dendritic shaft, whereas Ca2+ transients evoked by single EPSPs were largely restricted to a single active spine head. Calcium transients elicited in the active spines by a single AP or EPSP, in spines up to 80 μm for the soma, were of comparable amplitude. The Ca2+ transient in an active spine evoked by pairing an EPSP and a back-propagating AP separated by a time interval of 50 ms was larger if the AP followed the EPSP than if it preceded it. This difference reflected supra- and sublinear summation of Ca2+ transients, respectively. A comparable dependence of spinous Ca2+ transients on relative timing was observed also when short bursts of APs and EPSPs were paired. These results indicate that the amplitude of the spinous Ca2+ transients during coincident pre- and postsynaptic activity depended critically on the relative order of subthreshold EPSPs and back-propagating APs. Thus, in neocortical neurons the amplitude of spinous Ca2+ transients could encode small time differences between pre- and postsynaptic activity.
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Yasuna, J. A., and W. F. Hughes. "Squeeze Film Dynamics of Two-Phase Seals." Journal of Tribology 114, no. 2 (April 1, 1992): 236–46. http://dx.doi.org/10.1115/1.2920879.
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A dynamic analysis of two-phase face seals including squeeze film effects and thermal transients is presented. Axial responses to perturbations from equilibrium for various sets of typical seal operating conditions are examined, and the sensitivity of these responses to certain parameters is discussed. Sample calculations indicate damped transient responses which often decay as steady state is approached asymptotically. In some cases, however, stable and unstable oscillations are observed.
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Wiesner, T. F., B. C. Berk, and R. M. Nerem. "A mathematical model of cytosolic calcium dynamics in human umbilical vein endothelial cells." American Journal of Physiology-Cell Physiology 270, no. 5 (May 1, 1996): C1556—C1569. http://dx.doi.org/10.1152/ajpcell.1996.270.5.c1556.
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Important among the responses of endothelial cells are cytosolic free calcium transients. These transients are mediated by several factors, including blood-borne agonists, extracellular calcium, and fluid-imposed shear forces. The transients are characterized by a rapid rise followed by a plateau phase. A base mathematical model is presented that reasonably reproduces the measured calcium transient in cultured human umbilical vein endothelial cells responding to thrombin. Kinetic equations for receptor activation and calcium mobilization comprise the model. A graded response of intracellular free calcium to increasing concentrations of agonist is predicted. Also predicted is the elevation of the peak value and the plateau level by steady nonspecific leak of calcium across the plasma membrane. The influences of capacitative calcium entry, calcium-induced calcium release, and buffering by cytosolic proteins are investigated parametrically. The model predicts significant depletion of cellular calcium in response to agonist stimulation.
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Jean, NJ, and M. Gormley. "Modelling water trap seal boundary conditions in building drainage systems: Computational fluid dynamics analysis of unsteady friction to improve accuracy." Building Services Engineering Research and Technology 38, no. 5 (June 15, 2017): 580–601. http://dx.doi.org/10.1177/0143624417714930.
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The safe removal of disease-carrying human waste is the objective of all sanitation systems and the limiting of air pressure transients within the system remains a significant part of current codes and regulations. The water trap seal offers fundamental protection and is the system’s sole barrier between the public sewer network and habitable space inside a building. Modelling water trap seal responses to air pressure fluctuations offers an opportunity to analyse whole system performance, but the quality of the data depends on the accuracy of the modelling technique and that of the defining inputs. AIRNET, a 1D Method of Characteristics based model, enables rapid whole system testing; however, the present boundary condition for the water trap seal within the model is based solely on steady state conditions, ignoring system dynamics. Computational fluid dynamics offers an opportunity to numerically evaluate the flow patterns within the trap seal in response to applied air pressure transients. This research confirms the importance of the rate of rise, and hence frequency of air pressure transients incident on water trap seals and relates this to potential vulnerabilities of different device geometries, particularly the ratio between inner and outer wall length. The research led to the development of a dynamic velocity decrement model encapsulating unsteady friction and separation losses linked to device geometry for the first time. The development of a frequency-dependent internal energy term Δ v, suitable for inclusion in AIRNET provides the capability to predict more realistic water trap response to air pressure transients over a range of air pressure transient frequencies likely to cause problems: 1 Hz to 8 Hz. Practical application: Whole system modelling can greatly improve the ability of design engineers to fully simulate the operation of a building drainage system in a realistic way. The work described in this paper improves the accuracy of whole system models by evaluating water dynamic responses to air pressure transients using a range of techniques including computational fluid dynamics and more traditional 1D finite difference method of characteristics models. The work also paves the way for more robust evaluation of building drainage products through in-depth investigation of the fluid mechanics associated with their operation.
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Bignone, F. A., R. Livi, and M. Propato. "Long transients dynamics in biochemical networks." Il Nuovo Cimento D 20, no. 1 (January 1998): 91–102. http://dx.doi.org/10.1007/bf03036041.
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Shields, Monika W., Sara Hysong-Shimazu, Jason C. Shields, and Julie Woodruff. "Increased presence of mammal-eating killer whales in the Salish Sea with implications for predator-prey dynamics." PeerJ 6 (December 4, 2018): e6062. http://dx.doi.org/10.7717/peerj.6062.
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The inland waters of Washington State and southern British Columbia, collectively known as the Salish Sea, comprise key habitat for two regional populations of killer whales (Orcinus orca): the mammal-eating West Coast Transients and the endangered fish-eating Southern Residents. These two populations are genetically distinct and may avoid each other. Transient killer whale usage of the Salish Sea has been previously assessed over two seven-year time periods, showing an increase from 1987 to 2010. We documented a continued significant increase in mammal-eating killer whale presence in the Salish Sea from 2011 to 2017, with intra- and inter-annual variability and with record sightings in 2017. This continued increase, likely in response to abundant marine mammal prey, is related to both a growing population and an increase in the number of West Coast Transients visiting the area. Additionally, a negative binomial regression shows that absence of Southern Residents is correlated to transient presence. Finally, both populations of killer whales have been linked to regional harbor seal populations; harbor seals are salmonid-eating competitors of the Southern Residents and are prey for the mammal-eating transients. With Southern Residents listed as endangered, culling harbor seals has been proposed as a measure to help in their recovery. With this in mind, we developed an energetic model to assess the minimum number of harbor seals consumed by transient killer whales. Using the actual number of whales present in each age-sex class for each day of the year, we estimate that, at a minimum, transients in the Salish Sea consumed 1090 seals in 2017. This is more than 2% of the 2014 estimated harbor seal population the Salish Sea. The population controlling effects of transient killer whale predation on harbor seals should be considered when evaluating any pinniped management actions in the Salish Sea.
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Lindsey, C., and A. C. Donea. "What can He II 304 Å tell us about transient seismic emission from solar flares?" Proceedings of the International Astronomical Union 12, S327 (October 2016): 113–16. http://dx.doi.org/10.1017/s1743921317004525.
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AbstractAfter neary 20 years since their discovery by Kosovichev and Zharkova, the mechanics of the release of seismic transients into the solar interior from some flares remain a mystery. Seismically emissive flares invariably show the signatures of intense chromosphere heating consistent with pressure variations sufficient to drive seismic transients commensurate with helioseismic observations—under certain conditions. Magnetic observations show the signatures of apparent magnetic changes, suggesting Lorentz-force transients that could likewise drive seismic transients—similarly subject to certain conditions. But, the diagnostic signatures of both of these prospective drivers are apparent over vast regions from which no significant seismic emission emanates. What distinguishes the source regions of transient seismic emission from the much vaster regions that show the signatures of both transient heating and magnetic variations but are acoustically unproductive? Observations of acoustically active flares in He II 304 Å by the Atomospheric Imaging Assembly (AIA) aboard the Solar Dynamics Observatory (SDO) offer a promising new resource with which to address this question.
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Castellani, Francesco, Caterina Capponi, Bruno Brunone, Matteo Vedovelli, and Silvia Meniconi. "Performance Assessment of Pneumatic-Driven Automatic Valves to Improve Pipeline Fault Detection Procedure by Fast Transient Tests." Sensors 24, no. 6 (March 12, 2024): 1825. http://dx.doi.org/10.3390/s24061825.
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The use of fast transients for fault detection in long transmission networks makes the generation of controlled transients crucial. In order to maximise the information that can be extracted from the measured pressure time history (pressure signal), the transients must meet certain requirements. In particular, the manoeuvre that generates the transient must be fast and repeatable, and must produce a pressure wave that is as sharp as possible, without spurious pressure oscillations. This implies the use of small-diameter valves and often pneumatically operated automatic valves. In the present work, experimental transient tests are carried out at the Water Engineering Laboratory (WEL) of the University of Perugia using a butterfly valve and a ball pneumatic-driven valve to generate pressure waves in a pressurised copper pipe. A camera is used to monitor the valve displacement, while the pressure is measured by a pressure transducer close to the downstream end of the pipe where the pneumatic valve is installed. The experimental data are analysed to characterise the valve performance and to compare the two geometries in terms of valve closing dynamics, the sharpness of the generated pressure wave and the stability of the pressure time history. The present work demonstrates how the proposed approach can be very effective in easily characterising the transient dynamics.
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Zaki, Khaled, Yehya Imam, and Amgad El-Ansary. "Optimizing the dynamic response of pressure reducing valves to transients in water networks." Journal of Water Supply: Research and Technology-Aqua 68, no. 5 (May 6, 2019): 303–12. http://dx.doi.org/10.2166/aqua.2019.121.
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Abstract Pressure reducing valves (PRVs) are typically used to regulate excessive pressure in water distribution networks. During transient events, the dynamic response of PRVs may adversely affect pressure fluctuations in distribution networks. In this study, the dynamic response of PRVs was analyzed by developing a numerical model that coupled an existing water-hammer model and a two-parameter dynamic PRV model. PRV parameters were calibrated, and the model was validated using previous experimental observations. The model was then used to study the effect of PRV dynamics during transient events in a distribution network. To optimize the rate of PRV opening and closure and control its dynamic response, the model was interfaced with an optimization algorithm based on shuffled complex evolution. The applied objective function gave PRV parameters that accelerated damping of the transient pressure waves and minimized the root-mean-square deviation from post-transient steady pressure at all nodes in the network. The results of this study indicate the importance of accounting for PRV response when simulating transients in water distribution networks. This study also highlights the need for PRV manufacturers to include in their product catalogs dynamic PRV parameters for use in transient analysis.
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Cleuziou, Christophe, Stéphane Perrey, Fabio Borrani, Anne Marie Lecoq, Robin Candau, Daniel Courteix, and Philippe Obert. "Dynamic Responses of O2 Uptake at the Onset and End of Exercise in Trained Subjects." Canadian Journal of Applied Physiology 28, no. 4 (August 1, 2003): 630–41. http://dx.doi.org/10.1139/h03-048.
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Inconsistencies about dynamic asymmetry between the on- and off-transient responses in [Formula: see text] are found in the literature. Therefore the purpose of this study was to examine [Formula: see text]on- and off-transients during moderate- and heavy-intensity cycling exercise in trained subjects. Ten men underwent an initial incremental test for the estimation of ventilatory threshold (VT) and, on different days, two bouts of square-wave exercise at moderate (< VT) and heavy (> VT) intensities. [Formula: see text] kinetics in exercise and recovery were better described by a single exponential model (< VT), or by a double exponential with two time delays (> VT). For moderate exercise, we found a symmetry of [Formula: see text] kinetics between the on- and off-transients (i.e., fundamental component), consistent with a system manifesting linear control dynamics. For heavy exercise, a slow component superimposed on the fundamental phase was expressed in both the exercise and recovery, with similar parameter estimates. But the on-transient values of the time constant were appreciably faster than the associated off-transient, and independent of the work rate imposed (< VT and > VT). Our results do not support a dynamically linear system model of [Formula: see text] during cycling exercise in the heavy-intensity domain. Key words: oxygen uptake kinetics, on- and off-transients, slow component
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Cleuziou, Christophe, Stéphane Perrey, Fabio Borrani, Anne Marie Lecoq, Robin Candau, Daniel Courteix, and Philippe Obert. "Dynamic Responses of Oxygen Uptake at the Onset and End of Moderate and Heavy Exercise in Trained Subjects." Canadian Journal of Applied Physiology 29, no. 1 (February 1, 2004): 32–44. http://dx.doi.org/10.1139/h04-003.
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Inconsistencies about dynamic asymmetry between the on- and off-transient responses in [Formula: see text] are found in the literature. Therefore the purpose of this study was to examine [Formula: see text]on-and off-transients during moderate- and heavy-intensity cycling exercise in trained subjects. Ten men underwent an initial incremental test for the estimation of ventilatory threshold (VT) and, on different days, two bouts of square-wave exercise at moderate (< VT) and heavy (> VT) intensities. [Formula: see text] kinetics in exercise and recovery were better described by a single exponential model (< VT), or by a double exponential with two time delays (> VT). For moderate exercise, we found a symmetry of [Formula: see text] kinetics between the on- and off-transients (i.e., fundamental component), consistent with a system manifesting linear control dynamics. For heavy exercise, a slow component superimposed on the fundamental phase was expressed in both the exercise and recovery, with similar parameter estimates. But the on-transient values of the time constant were appreciably faster than the associated off-transient, and independent of the work rate imposed (< VT and > VT). Our results do not support a dynamically linear system model of [Formula: see text] during cycling exercise in the heavy-intensity domain. Key words: oxygen uptake kinetics, on- and off-transients, slow component
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Zhao, Tian Yang, Dan Jiang, Song Yu, Jie Wang, and Ping Yang. "Analysis of High Pressure Transients in Water Hydraulic Pipeline Using Matlab/Simulink." Key Engineering Materials 621 (August 2014): 311–16. http://dx.doi.org/10.4028/www.scientific.net/kem.621.311.
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Based on the continuity equation and the motion equation of fluid dynamics, a mathematical model of high pressure transients in water hydraulic pipeline is presented. In the model, the friction item is consist of steady friction item and dynamic friction item, using the Darcy-Weisbach equation to solve steady viscous friction item and using four exponential terms instead of weighting function to solve dynamic friction item. By finite difference method accompanied with Matlab/Simulink, an example of high pressure turbulent flow in water hydraulic pipeline is configured so as to simulate the dynamic characteristics of pressure transients. The comparison between the observed result and the simulation result shows the mathematical model of high pressure transients in water hydraulic pipeline with turbulent flow is reasonable.
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Cisneros MAGAÑA, Rafael, and Jose Ortiz Bejar. "DYNAMIC MODELLING OF THREE-PHASE MICROGRIDS INCLUDING DQ0 CURRENT CONTROLLED PHOTOVOLTAIC GENERATION UNDER TRANSIENT CONDITIONS." DYNA ENERGIA Y SOSTENIBILIDAD 13, no. 1 (July 24, 2024): [15P.]. http://dx.doi.org/10.52152/des11228.
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ABSTRACT: The photovoltaic generation can be interconnected to power systems or to insulated grids to satisfy the growing electrical demand as an alternative renewable energy source. The photovoltaic generator dynamics affects the control, protection, stability, and power quality of the electrical grid, this network dynamics requires to be examined and conveniently regulated and adjusted. The dynamic averaged model for the dq0 current controlled DC/AC inverter is applied to obtain the time-domain response to electromagnetic transients under special conditions such as electrical load fluctuations, unbalanced faults, voltage and current transients to verify e.g., the ride through capability or to adjust the protection and control devices, these transients can be present during the operation of electrical microgrids and power systems interconnected with photovoltaic generation. The system modelling includes the photovoltaic plant interconnected with the microgrid using the dq0 current controlled DC/AC inverter. The case studies are applied to analyse three-phase electrical microgrids, their time-domain response, and the obtained voltage and current waveforms can be used to verify the dynamic behaviour and stability of the electrical system interconnected with photovoltaic generation and similarly to verify the operation of the dq0 current controller for the inverter. The results can be used to control the microgrid dynamic behaviour. Keywords: current control, dq0 transform, inverter, microgrids, photovoltaic generation, power quality, protection, time-domain, transients, unbalanced faults, unbalanced voltage sags, voltage source converter
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Mar, D. J., L. M. Pecora, F. J. Rachford, and T. L. Carroll. "Dynamics of transients in yttrium-iron-garnet." Chaos: An Interdisciplinary Journal of Nonlinear Science 7, no. 4 (December 1997): 803–9. http://dx.doi.org/10.1063/1.166280.
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Friston, Karl J. "The labile brain. II. Transients, complexity and selection." Philosophical Transactions of the Royal Society of London. Series B: Biological Sciences 355, no. 1394 (February 29, 2000): 237–52. http://dx.doi.org/10.1098/rstb.2000.0561.
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The successive expression of neuronal transients is related to dynamic correlations and, as shown in this paper, to dynamic instability. Dynamic instability is a form of complexity, typical of neuronal systems, which may be crucial for adaptive brain function from two perspectives. The first is from the point of view of neuronal selection and self–organizing systems: if selective mechanisms underpin the emergence of adaptive neuronal responses then dynamic instability is, itself, necessarily adaptive. This is because dynamic instability is the source of diversity on which selection acts and is therefore subject to selective pressure. In short, the emergence of order, through selection, depends almost paradoxically on the instabilities that characterize the diversity of brain dynamics. The second perspective is provided by information theory.
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Pannila, Earl A. R. L., and Mahesh Edirisinghe. "Signatures of Transient Overvoltages in Low Voltage Power Systems in Tea Factories and Their Implications on Insulation Deterioration and Allied Power Quality Issues." Journal of Electrical and Computer Engineering 2021 (November 19, 2021): 1–12. http://dx.doi.org/10.1155/2021/2623965.
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Electrical equipment and supply cables demand a better quality of supply, with the recent advancements in integrated sensitive solid-state controls. Divergently, proliferated heavy inductive motors and some performance additions based on power electronics have introduced power quality issues to the network. Thus, this study mainly investigates the impact of switching transients generated by electromechanical machines in industrial power systems on insulation deterioration while taking transient overvoltages due to capacitor bank switching also to support. Transients with a high rate of rise are likely to catalyze the degradation of the insulation quality and break down the insulating material through ionization. These steeply passing overvoltage stresses let partial discharges ensue, which can attack the insulation over long service. To unveil this danger, 314 common-mode transient waveforms were measured in the electrical machines of five tea factories in Sri Lanka, in a 50 ms measurement window, taken in 55 measuring attempts. Most of the transients observed are in the form of a damped oscillatory waveform tailed by fast exponential collapse. That correlates to insulation degradation having a very steep rise as 30.04 V/ns, the highest at the withering section. When machines are heavily loaded, situations tend to generate transients with high amplitudes. There were transient bursts that spread as 426.3 ms, while 14 ns fast rise times were recorded from withering motors. Unlike electrical resonance and power-frequency overvoltages, electromagnetic switching transients last even less than 100 ms. To underline this, an analysis of the frequency domain of transients was also presented, which proves high density of high-frequency components reaching 107 kHz range. Accepting the fact that frequency and amplitude are always under the influences of innumerable dynamics, the observational evidence of the study endorses that electrical stress built by the transient nature of the factories reduces the life expectancy of electrical insulation.
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Alleyne, Andrew, and Neera Jain. "Transient Thermal Systems: Dynamics and Control." Mechanical Engineering 136, no. 03 (March 1, 2014): S4—S12. http://dx.doi.org/10.1115/1.2014-mar-4.
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This is a study focused on the criticality of thermal systems in almost every domain of energy conversion. Thermal systems are critically important to nearly all domains of energy conversion, and controls are vital to extracting maximal efficiency from the overall system. Understanding the dynamics of transient thermal systems is the first step towards effective control design. While a great deal of understanding of steady-state performance of an overall system already exists, the combined performance of coupled and interconnected systems during transients is still not well described or understood. This becomes more important with increased system complexity or increased transient relevance. Continued improvement in control-oriented modeling will be very valuable in terms of accuracy, speed, etc. With energy as a crucial theme for a sustainable future, it is clear that the Mechanical Engineering community must play a key leadership role in achieving this potential, since the thermal energy domain is one with which we are most familiar.
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Bousbia-Salah, Anis. "Assessment of water hammer effects on boiling water nuclear reactor core dynamics." Nuclear Technology and Radiation Protection 22, no. 1 (2007): 18–33. http://dx.doi.org/10.2298/ntrp0701018b.
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Complex phenomena, as water hammer transients, occurring in nuclear power plants are still not very well investigated by the current best estimate computational tools. Within this frame work, a rapid positive reactivity addition into the core generated by a water hammer transient is considered. The numerical simulation of such phenomena was carried out using the coupled RELAP5/PARCS code. An over all data comparison shows good agreement between the calculated and measured core pressure wave trends. However, the predicted power response during the excursion phase did not correctly match the experimental tendency. Because of this, sensitivity studies have been carried out in order to identify the most influential parameters that govern the dynamics of the power excursion. After investigating the pressure wave amplitude and the void feed back responses, it was found that the disagreement between the calculated and measured data occurs mainly due to the RELAP5 low void condensation rate which seems to be questionable during rapid transients. .
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Delorey, Andrew A., Kevin Chao, Kazushige Obara, and Paul A. Johnson. "Cascading elastic perturbation in Japan due to the 2012 Mw 8.6 Indian Ocean earthquake." Science Advances 1, no. 9 (October 2015): e1500468. http://dx.doi.org/10.1126/sciadv.1500468.
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Since the discovery of extensive earthquake triggering occurring in response to the 1992 Mw (moment magnitude) 7.3 Landers earthquake, it is now well established that seismic waves from earthquakes can trigger other earthquakes, tremor, slow slip, and pore pressure changes. Our contention is that earthquake triggering is one manifestation of a more widespread elastic disturbance that reveals information about Earth’s stress state. Earth’s stress state is central to our understanding of both natural and anthropogenic-induced crustal processes. We show that seismic waves from distant earthquakes may perturb stresses and frictional properties on faults and elastic moduli of the crust in cascading fashion. Transient dynamic stresses place crustal material into a metastable state during which the material recovers through a process termed slow dynamics. This observation of widespread, dynamically induced elastic perturbation, including systematic migration of offshore seismicity, strain transients, and velocity transients, presents a new characterization of Earth’s elastic system that will advance our understanding of plate tectonics, seismicity, and seismic hazards.
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Zaytsev, Nikolay, Andrey Bondarenko, and Dmitriy Pyankov. "SIMULATION OF DYNAMICS OF THE SWIVEL CONTROL NOZZLE WITH DOUBLE ELASTIC JOINT." Perm National Research Polytechnic University Aerospace Engineering Bulletin, no. 60 (2020): 34–44. http://dx.doi.org/10.15593/2224-9982/2020.60.04.
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In order to create control moments for the rocket, the design of modern solid propellant rocket engines uses swivel control nozzles with elastic support joint. The disadvantage of such a joint as the nozzle suspension is the high joint torque, which determines the high requirements for power and effort of steering actuators. In order to reduce these requirements, it is possible to use the design of a swivel control nozzle with a double elastic joint, known as a nozzle with double elastic seal. This nozzle is not used due to its design and operational complexity, particularly due to its tendency to oscillatory processes, as it is a dynamic system with two degrees of freedom. In the article numerical simulation of dynamics of transient modes at deviations on demanded angles of a swivel control nozzle with double elastic joint is considered. For this purpose the approximate nonlinear mathematical model of dynamics of this nozzle constructed by the Lagrange method is used. The results of numerical simulation of transients in the open loop channel of nozzle movement control at abruptly apply the constant effort of steering actuator are given. It is given the method of determination the values of rotation angles of the moving parts of a nozzle and the effort of a steering actuators corresponding to the required angle of rotation of the nozzle. For the given values of the design characteristics of the nozzle and the layout parameters of the nozzle-steering actuators system by numerical simulation it is established that an acceptable oscillation of transients for the nozzle with a double elastic joint can be achieved by increasing the viscosity resistance coefficients in its suspension. Significant influence on damping of oscillations in transient modes of dynamics of the swivel control nozzle of its damping joint moments is also shown.
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Oggioni, Carlo, Chris Keckler, and Massimiliano Fratoni. "ANALYSIS OF MODIFIED PASSIVE SAFETY SYSTEM IN FAST RECTORS TRANSIENTS." EPJ Web of Conferences 247 (2021): 07016. http://dx.doi.org/10.1051/epjconf/202124707016.
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The Autonomous Reactivity Control (ARC) system is a passive safety system aiming to provide an additional negative reactivity feedback during reactor transient scenarios. This paper shows how the performance of the ARC system can be enhanced by introducing a hydraulic diode that allows for different engagement and disengagement speeds of system. The benefits of the proposed system is assessed in a reference soidum-cooled fast reactor (SFR) during multiple postulated transient scenarios. The reactor and plant dynamic response are evaluated using SAS4A/SASSYS-1, whereas for the internal ARC system fluid dynamics, the SAM code is adopted. The two codes are externally coupled using a custom driver script which coordinates data exchange and restart calculations at each time step, with Picard iterations used to converge each time step. All the transients analyzed in this work show that the enhanced ARC system is effective in reducing peak temperatures and in reducing the oscillatory behavior encountered in some cases with the standard ARC system.
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Luo, Y., R. Cooke, and E. Pate. "A model of stress relaxation in cross-bridge systems: effect of a series elastic element." American Journal of Physiology-Cell Physiology 265, no. 1 (July 1, 1993): C279—C288. http://dx.doi.org/10.1152/ajpcell.1993.265.1.c279.
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Many experimental protocols employed in the study of muscle mechanics use tension transients as a probe of the magnitudes of the kinetic rates in the underlying cross-bridge dynamics. These transients could potentially be modified by the elastic elements that exist both within the fiber and at the points of attachment to the experimental apparatus. To better understand the magnitude of such modifications, we have used computer simulation to investigate the transients that would be expected for cross bridges acting on an actin filament attached to an elastic element. The original model of cross-bridge mechanics by A.F. Huxley was used (Prog. Biophys. 7: 255-318, 1957). After an isometric equilibrium is achieved, a tension transient is produced by changing the dissociation rate constant, g1, while holding the attachment rate constant, f1, fixed. This decreases the number of attached, force-producing cross bridges. We find that the tension transients are markedly slowed by the presence of even a few (> or = 2) nanometers of series elastic strain per half-sarcomere. Thus some rate constants inferred from mechanical transients (e.g., those induced by caged ligands) may underestimate the actual kinetic rates of the cross-bridge processes.
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Baumann, Markus, Christian Koch, and Stephan Staudacher. "Application of Neural Networks and Transfer Learning to Turbomachinery Heat Transfer." Aerospace 9, no. 2 (January 20, 2022): 49. http://dx.doi.org/10.3390/aerospace9020049.
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Model-based predictive maintenance using high-frequency in-flight data requires digital twins that can model the dynamics of their physical twin with high precision. The models of the twins need to be fast and dynamically updatable. Machine learning offers the possibility to address these challenges in modeling the transient performance of aero engines. During transient operation, heat transferred between the engine’s structure and the annulus flow plays an important role. Diabatic performance modeling is demonstrated using non-dimensional transient heat transfer maps and transfer learning to extend turbomachinery transient modeling. The general form of such a map for a simple system similar to a pipe is reproduced by a Multilayer Perceptron neural network. It is trained using data from a finite element simulation. In a next step, the network is transferred using measurements to model the thermal transients of an aero engine. Only a limited number of parameters measured during selected transient maneuvers is needed to generate suitable non-dimensional transient heat transfer maps. With these additional steps, the extended performance model matches the engine thermal transients well.
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Foster, E. A. D. "A Causal Bifurcation Sequence Producing a Chaotic Transient Regime." International Journal of Bifurcation and Chaos 07, no. 02 (February 1997): 319–30. http://dx.doi.org/10.1142/s0218127497000212.
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An organized sequence of codimension-1 bifurcations is investigated. This bifurcation sequence is shown to be generic for a class of noninvertible scalar maps containing symmetry, and is believed to occur commonly in both discrete and continuous dynamical systems. Particular dynamics are specified initially, in which chaotic sets with symmetry evolve from attracting to transients and back to attracting. The required dynamics limit the bifurcation structures possible, which in turn constrain the functional form of the dynamical system. The canonical scalar map producing these dynamics is determined to be quintic and odd symmetric. Analysis includes a discussion of the structure of the chaotic transient regime, description of the bifurcation sequence corresponding to full dynamics, and a complete classification of bifurcation sequences producing associated partial dynamics.
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Moen, J., D. Evans, H. C. Carlson, and M. Lockwood. "Dayside moving auroral transients related to LLBL dynamics." Geophysical Research Letters 23, no. 22 (November 1, 1996): 3247–50. http://dx.doi.org/10.1029/96gl02766.
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Špička, Václav, Bedřich Velický, and Anděla Kalvová. "Long and short time quantum dynamics: III. Transients." Physica E: Low-dimensional Systems and Nanostructures 29, no. 1-2 (October 2005): 196–212. http://dx.doi.org/10.1016/j.physe.2005.05.016.
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Kurtyka, Bogdan, Milliana Kaisheva, and Robert de Levie. "On interfacial dynamics: capacitance transients accompanying partial desorption." Journal of Electroanalytical Chemistry 341, no. 1-2 (December 1992): 343–51. http://dx.doi.org/10.1016/0022-0728(92)80492-m.
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Ramadoss, Janarthan, Premraj Durairaj, Karthikeyan Rajagopal, and Akif Akgul. "Collective Dynamical Behaviors of Nonlocally Coupled Brockett Oscillators." Mathematical Problems in Engineering 2023 (April 17, 2023): 1–7. http://dx.doi.org/10.1155/2023/1600610.
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In this study, we consider a network of nonlocally coupled Brockett oscillators (BOs) with attractive and repulsive (AR) couplings to illustrate the existence of diverse collective dynamical behaviors, whereas previous studies solely concentrated on synchronization. In the absence of coupling, the individual BO oscillator shows stable periodic oscillations (POs) or stable steady state (SS) depending on the critical values of the parameters. We first begin by examining the collective dynamics by setting the critical value of the parameters at the active (PO) region. A diverge collective dynamical states are manifested for a fixed nonlocal coupling range with rising coupling magnitude. Notably, the lower coupling strength exhibits two distinct dynamical patterns at lower and higher transients. At lesser transients, for example, transient dynamics of desynchronization, chimera, and traveling wave states are observed. At larger time periods, the transient dynamics disappear with the emergence of a synchronized state. Increasing the coupling strength results in a unique state of traveling wave or synchronized state for smaller and larger time periods depending on the coupling strength. Increasing the coupling strength further gives rise to clustering behaviors. Importantly, the considered system attains cluster oscillation death (COD) through a cluster oscillatory state (COS). Finally, there exists a chimera death at a larger coupling strength. The observed dynamical transitions are further demonstrated through the two-parameter analysis by setting different critical thresholds.
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Moody, Sohie Lee, and David Zipser. "A Model of Reaching Dynamics in Primary Motor Cortex." Journal of Cognitive Neuroscience 10, no. 1 (January 1998): 35–45. http://dx.doi.org/10.1162/089892998563761.
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Features of virtually all voluntary movements are represented in the primary motor cortex. The movements can be ongoing, imminent, delayed, or imagined. Our goal was to investigate the dynamics of movement representation in the motor cortex. To do this we trained a fully recurrent neural network to continually output the direction and magnitude of movements required to reach randomly changing targets. Model neurons developed preferred directions and other properties similar to real motor cortical neurons. The key finding is that when the target for a reaching movement changes location, the ensemble representation of the movement changes nearly monotonically, and the individual neurons comprising the representation exhibit strong, nonmonotonic transients. These transients serve as internal recurrent signals that force the ensemble representation to change more rapidly than if it were limited by the time constants of individual neurons. These transients, if they exist, could be observed in experiments that require only slight modifications of the standard paradigm used to investigate movement representation in the motor cortex.
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SARDANYÉS, JOSEP, and ERNEST FONTICH. "ON THE METAPOPULATION DYNAMICS OF AUTOCATALYSIS: EXTINCTION TRANSIENTS RELATED TO GHOSTS." International Journal of Bifurcation and Chaos 20, no. 04 (April 2010): 1261–68. http://dx.doi.org/10.1142/s0218127410026460.
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One of the theoretical approaches to study spatially-extended ecosystems is given by metapopulation models, which consider fragmented populations inhabiting discrete patches linked by migration. Most of the metapopulation models assume exponential growth of the local populations and few works have explored the role of cooperation in fragmented ecosystems. In this letter, we study the dynamics and the bifurcation scenarios of a minimal, two-patch metapopulation Turing-like model given by nonlinear differential equations with an autocatalytic reaction term together with diffusion. We also analyze the extinction transients of the metapopulations focusing on the effect of coupling two local populations undergoing delayed transition phenomena due to ghost saddle remnants. We find that increasing diffusion rates enhance the delaying capacity of the ghosts. We finally propose the saddle remnant as a new class of transient generator mechanism for ecological systems.
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Panayotova, Iordanka N., and Kyle L. Swanson. "Edge Wave Asymmetries." Journal of the Atmospheric Sciences 63, no. 4 (April 1, 2006): 1357–64. http://dx.doi.org/10.1175/jas3618.1.
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Abstract Meridional asymmetry arising from the inclusion of meridional variation in the Coriolis parameter is shown to be a fundamental property of the higher-order dynamics of Eady edge waves. This asymmetry may be relevant to structural characteristics of observed atmospheric transients, particularly short waves propagating along the extratropical dynamic tropopause.
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Nakamura, Tsutomu, Osamu Abe, Natsuo Numano, and Theodore E. Lang. "Computer Study of Snow Avalanche Startup Dynamics." Annals of Glaciology 6 (1985): 15–18. http://dx.doi.org/10.3189/1985aog6-1-15-18.
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The startup dynamics of three wet snow avalanches in central Japan were evaluated by computer modeling the occurrences and comparing leading edge position-time data. Results were compared between three finite difference based computer codes, which were used to model the startup transients. Two of the computer codes use equations of uniform flow hydrodynamics, the third uses transient viscous fluid mechanics. The latter two codes also incorporate a material description of snow as a locking material. Results show a general increasing of frictional and/or viscous coefficients in the avalanche startup zones in order to match the kinematics of startup. Differences in results between the codes is attributed to the shape of the startup zones, whether convex or concave. The results indicate the magnitude of perturbation of startup on total avalanche runout time, which is likely to be negligible on long-duration avalanche occurrences.
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Nakamura, Tsutomu, Osamu Abe, Natsuo Numano, and Theodore E. Lang. "Computer Study of Snow Avalanche Startup Dynamics." Annals of Glaciology 6 (1985): 15–18. http://dx.doi.org/10.1017/s0260305500009903.
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The startup dynamics of three wet snow avalanches in central Japan were evaluated by computer modeling the occurrences and comparing leading edge position-time data. Results were compared between three finite difference based computer codes, which were used to model the startup transients. Two of the computer codes use equations of uniform flow hydrodynamics, the third uses transient viscous fluid mechanics. The latter two codes also incorporate a material description of snow as a locking material. Results show a general increasing of frictional and/or viscous coefficients in the avalanche startup zones in order to match the kinematics of startup. Differences in results between the codes is attributed to the shape of the startup zones, whether convex or concave. The results indicate the magnitude of perturbation of startup on total avalanche runout time, which is likely to be negligible on long-duration avalanche occurrences.
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CRIMINALE, W. O., T. L. JACKSON, D. G. LASSEIGNE, and R. D. JOSLIN. "Perturbation dynamics in viscous channel flows." Journal of Fluid Mechanics 339 (May 25, 1997): 55–75. http://dx.doi.org/10.1017/s0022112097005235.
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Plane viscous channel flows are perturbed and the ensuing initial-value problems are investigated in detail. Unlike traditional methods where travelling wave normal modes are assumed as solutions, this work offers a means whereby arbitrary initial input can be specified without having to resort to eigenfunction expansions. The full temporal behaviour, including both early-time transients and the long-time asymptotics, can be determined for any initial small-amplitude three-dimensional disturbance. The bases for the theoretical analysis are: (a) linearization of the governing equations; (b) Fourier decomposition in the spanwise and streamwise directions of the flow; and (c) direct numerical integration of the resulting partial differential equations. All of the stability criteria that are known for such flows can be reproduced. Also, optimal initial conditions measured in terms of the normalized energy growth can be determined in a straightforward manner and such optimal conditions clearly reflect transient growth data that are easily determined by a rational choice of a basis for the initial conditions. Although there can be significant transient growth for subcritical values of the Reynolds number, it does not appear possible that arbitrary initial conditions will lead to the exceptionally large transient amplitudes that have been determined by optimization of normal modes when used without regard to a particular initial-value problem. The approach is general and can be applied to other classes of problems where only a finite discrete spectrum exists (e.g. the Blasius boundary layer). Finally, results from the temporal theory are compared with the equivalent transient test case in the spatially evolving problem with the spatial results having been obtained using both a temporally and spatially accurate direct numerical simulation code.
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Antosiewicz, Jan, and Dietmar Porschke. "Brownian dynamics simulation of electrooptical transients for complex macrodipoles." Journal of Physical Chemistry 97, no. 11 (March 1993): 2767–73. http://dx.doi.org/10.1021/j100113a046.
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Franaszek, Marek, and Heikki M. Isomäki. "Anomalous chaotic transients and repellers of bouncing-ball dynamics." Physical Review A 43, no. 8 (April 1, 1991): 4231–36. http://dx.doi.org/10.1103/physreva.43.4231.
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