scholarly journals Unifying deterministic and stochastic ecological dynamics via a landscape-flux approach

2021 ◽  
Vol 118 (24) ◽  
pp. e2103779118
Author(s):  
Li Xu ◽  
Denis Patterson ◽  
Ann Carla Staver ◽  
Simon Asher Levin ◽  
Jin Wang
Keyword(s):  
Deterministic Model ◽  
Stable State ◽  
Quantitative Measure ◽  
Entropy Production Rate ◽  
Stable States ◽  
Steady State Probability ◽  
Ecological Dynamics ◽  
Frequency Distributions ◽  
Population Potential ◽  
Potential Landscape

The frequency distributions can characterize the population-potential landscape related to the stability of ecological states. We illustrate the practical utility of this approach by analyzing a forest–savanna model. Savanna and forest states coexist under certain conditions, consistent with past theoretical work and empirical observations. However, a grassland state, unseen in the corresponding deterministic model, emerges as an alternative quasi-stable state under fluctuations, providing a theoretical basis for the appearance of widespread grasslands in some empirical analyses. The ecological dynamics are determined by both the population-potential landscape gradient and the steady-state probability flux. The flux quantifies the net input/output to the ecological system and therefore the degree of nonequilibriumness. Landscape and flux together determine the transitions between stable states characterized by dominant paths and switching rates. The intrinsic potential landscape admits a Lyapunov function, which provides a quantitative measure of global stability. We find that the average flux, entropy production rate, and free energy have significant changes near bifurcations under both finite and zero fluctuation. These may provide both dynamical and thermodynamic origins of the bifurcations. We identified the variances in observed frequency time traces, fluctuations, and time irreversibility as kinematic measures for bifurcations. This framework opens the way to characterize ecological systems globally, to uncover how they change among states, and to quantify the emergence of quasi-stable states under stochastic fluctuations.

scholarly journals Path-dependent institutions drive alternative stable states in conservation

2018 ◽  
Vol 116 (2) ◽  
pp. 689-694 ◽  
Author(s):  
Edward W. Tekwa ◽  
Eli P. Fenichel ◽  
Simon A. Levin ◽  
Malin L. Pinsky
Keyword(s):  
Renewable Resources ◽  
Path Dependence ◽  
Alternative Stable States ◽  
Stable State ◽  
Empirical Support ◽  
Stable States ◽  
Alternative Stable State ◽  
Important Challenge ◽  
Quantitative Analyses ◽  
Path Dependent

Understanding why some renewable resources are overharvested while others are conserved remains an important challenge. Most explanations focus on institutional or ecological differences among resources. Here, we provide theoretical and empirical evidence that conservation and overharvest can be alternative stable states within the same exclusive-resource management system because of path-dependent processes, including slow institutional adaptation. Surprisingly, this theory predicts that the alternative states of strong conservation or overharvest are most likely for resources that were previously thought to be easily conserved under optimal management or even open access. Quantitative analyses of harvest rates from 217 intensely managed fisheries supports the predictions. Fisheries’ harvest rates also showed transient dynamics characteristic of path dependence, as well as convergence to the alternative stable state after unexpected transitions. This statistical evidence for path dependence differs from previous empirical support that was based largely on case studies, experiments, and distributional analyses. Alternative stable states in conservation appear likely outcomes for many cooperatively managed renewable resources, which implies that achieving conservation outcomes hinges on harnessing existing policy tools to navigate transitions.

Design and Characterization of Single Beam for Latching Electrothermal Microswitch

2012 ◽  
Vol 468-471 ◽  
pp. 286-289
Author(s):  
Ying Zhang ◽  
Hong Wang ◽  
Yan Wang ◽  
Sheng Ping Mao ◽  
Gui Fu Ding
Keyword(s):  
Mechanical Performance ◽  
Stable State ◽  
Cantilever Beams ◽  
Analysis Software ◽  
Stable States ◽  
Element Analysis ◽  
Single Beam ◽  
Fabrication And Characterization ◽  
Continuous Power

This paper presents the design, fabrication and characterization of single beam for latching electrothermal microswitch. This microswitch consists of two cantilever beams using bimorph electrothermal actuator with mechanical latching for performing low power bistable relay applications. A stable state can be acquired without continuous power which is only needed to switch between two stable states of the microactuator. The single beam is discussed mainly to judge the possibility of realizing the designed function. First, reasonable shape of the resistance is designed using finite element analysis software ANSYS. Then, mechanical performance was characterized by WYKO NT1100 optical profiling system, the tip deflection of single beam can meet the designed demand.

Automated modal parameters identification of bistable composite plate using two-stage clustering of operational modal testing

2020 ◽  
pp. 002199832090308
Author(s):  
Mahdi Ghamami ◽  
Hassan Nahvi ◽  
Vahid Yaghoubi
Keyword(s):  
Analytical Method ◽  
Composite Plate ◽  
Ritz Method ◽  
Stable State ◽  
User Interaction ◽  
Modal Testing ◽  
Modal Parameters ◽  
Identification Algorithm ◽  
Stable States ◽  
Modal Parameters Identification

In recent years, smart structures have attracted much interest as morphing structures. One of the simplest types of these structures is bistable composite plate, which has many applications in aerospace, structures, actuators, etc. On the other hand, inverse problem theory provides conceptual ideas and methods for the practical solution of applied problems. These methods are opposite of the forward problem and define a model of the system based on output or observations. In this paper, a modified identification algorithm is used to determine the modal parameters of a bistable composite plate based on vibrational signals. Both analytical and experimental approaches have been considered and analytical method has been used to investigate the accuracy of identification algorithm, which has been performed based on experimental measurement. In the analytical method, static and free vibration behaviors of a cross-ply bistable composite plate are studied by the Hamilton's principle and the Rayleigh–Ritz method. The experimental approach is performed by an operational modal testing, which is a nondestructive test. The identification process does not require user interaction and the process uses only a single dataset and there is no need to repeat the test or data collection. The advantages of the proposed algorithm is the ability to determine the modal parameters of each stable state with high accuracy and robustness. A comparison of the natural frequencies shows that the identification of both stable states has been successful and the estimated modal parameters are in good agreement with the analytical and experimental results.

scholarly journals A Nonvolatile Fractional Order Memristor Model and its Complex Dynamics

Entropy ◽  
2019 ◽  
Vol 21 (10) ◽  
pp. 955 ◽  
Author(s):  
Wu ◽  
Wang ◽  
Iu ◽  
Shen ◽  
Zhou
Keyword(s):  
Fractional Order ◽  
Complex Dynamics ◽  
Equilibrium Points ◽  
Stable State ◽  
Electrical Characteristics ◽  
Chaotic Circuit ◽  
Stable States ◽  
Road Map ◽  
Chaotic Circuits ◽  
Integral Order

It is found that the fractional order memristor model can better simulate the characteristics of memristors and that chaotic circuits based on fractional order memristors also exhibit abundant dynamic behavior. This paper proposes an active fractional order memristor model and analyzes the electrical characteristics of the memristor via Power-Off Plot and Dynamic Road Map. We find that the fractional order memristor has continually stable states and is therefore nonvolatile. We also show that the memristor can be switched from one stable state to another under the excitation of appropriate voltage pulse. The volt–ampere hysteretic curves, frequency characteristics, and active characteristics of integral order and fractional order memristors are compared and analyzed. Based on the fractional order memristor and fractional order capacitor and inductor, we construct a chaotic circuit, of which the dynamic characteristics with respect to memristor’s parameters, fractional order α, and initial values are analyzed. The chaotic circuit has an infinite number of equilibrium points with multi-stability and exhibits coexisting bifurcations and coexisting attractors. Finally, the fractional order memristor-based chaotic circuit is verified by circuit simulations and DSP experiments.

A Criteria for Size Separation Using Maximum Entropy Production

2009 ◽  
Author(s):  
Chuan-ping Liu ◽  
Li Wang ◽  
Min Jia ◽  
Lige Tong
Keyword(s):  
Entropy Production ◽  
Maximum Entropy ◽  
Stable State ◽  
Irreversible Processes ◽  
Entropy Production Rate ◽  
Absolute Maximum ◽  
Kinetic Temperature ◽  
Granular Mixture ◽  
Maximum Entropy Production ◽  
Size Separation

In order to study analytically the nature of the size separation in granular mixture, we present the maximum entropy production principle based on kinetic temperature of granular mixture. For simplicity we apply this principle to size separation of a sphere binary mixture in vibrated bed, and we find a new thermodynamic mechanism of size separation phenomenon. With the irreversible processes such as elastic collisions and frictions, the kinetic energy is dissipated rapidly in system, which induces the entropy production. By the fact that the entropy production rate always has the absolute maximum at the stable state of granular mixture, we find the crossover from “Brazil Nut Effect” to its reverse by changing particles size and density, and our result is about satisfied with Schnautz’s experiment.

scholarly journals The importance of transient social dynamics for restoring ecosystems beyond ecological tipping points

2020 ◽  
Vol 117 (5) ◽  
pp. 2717-2722 ◽  
Author(s):  
Romina Martin ◽  
Maja Schlüter ◽  
Thorsten Blenckner
Keyword(s):  
Policy Making ◽  
Sewage Treatment ◽  
Stable State ◽  
Social Processes ◽  
Transient Dynamics ◽  
Time Lags ◽  
Tipping Points ◽  
Stable States ◽  
Social Ecological ◽  
Restoration Time

Regime shift modeling and management generally focus on tipping points, early warning indicators, and the prevention of abrupt shifts to undesirable states. Few studies assess the potential for restoring a deteriorating ecosystem that is on a transition pathway toward an undesirable state. During the transition, feedbacks that stabilize the new regime are still weak, providing an opportunity to reverse the ongoing shift. Here, we present a social-ecological model that explores both how transient social processes affect ecological dynamics in the vicinity of a tipping point to reinforce the desired state and how social mechanisms of policy implementation affect restoration time. We simulate transitions of a lake, policy making, and behavioral change by lake polluters to study the time lags that emerge as a response to the transient, deteriorating lake state. We found that restoration time is most sensitive to the timing of policy making, but that the transient dynamics of the social processes determined outcomes in nontrivial ways. Social pressure to adopt costly technology, in our case on-site sewage treatment, was up to a degree capable of compensating for delays in municipal policy making. Our analysis of interacting social and ecological time lags in the transient phase of a shallow lake highlights opportunities for restoration that a stable state analysis would miss. We discuss management perspectives for navigating critical feedbacks in a transitioning social-ecological system. The understanding of transient dynamics and the interaction with social time lags can be more relevant than solely stable states and tipping points.

scholarly journals Numerical and experimental analysis of the bi-stable state for frictional continuous system

2020 ◽  
Vol 102 (3) ◽  
pp. 1361-1374
Author(s):  
D. Tonazzi ◽  
M. Passafiume ◽  
A. Papangelo ◽  
N. Hoffmann ◽  
F. Massi
Keyword(s):  
Stable State ◽  
Continuous System ◽  
External Perturbation ◽  
Element Model ◽  
Dynamical Response ◽  
Continuous Systems ◽  
Sliding Velocity ◽  
Stable States ◽  
Stick Slip ◽  
Stable Solutions

AbstractUnstable friction-induced vibrations are considered an annoying problem in several fields of engineering. Although several theoretical analyses have suggested that friction-excited dynamical systems may experience sub-critical bifurcations, and show multiple coexisting stable solutions, these phenomena need to be proved experimentally and on continuous systems. The present work aims to partially fill this gap. The dynamical response of a continuous system subjected to frictional excitation is investigated. The frictional system is constituted of a 3D printed oscillator, obtained by additive manufacturing that slides against a disc rotating at a prescribed velocity. Both a finite element model and an experimental setup has been developed. It is shown both numerically and experimentally that in a certain range of the imposed sliding velocity the oscillator has two stable states, i.e. steady sliding and stick–slip oscillations. Furthermore, it is possible to jump from one state to the other by introducing an external perturbation. A parametric analysis is also presented, with respect to the main parameters influencing the nonlinear dynamic response, to determine the interval of sliding velocity where the oscillator presents the two stable solutions, i.e. steady sliding and stick–slip limit cycle.

Thermodynamics of Homogeneous Nucleation under Different Constraints

2001 ◽  
Vol 215 (9) ◽  
Author(s):  
W. Vogelsberger
Keyword(s):  
Potential Function ◽  
Condensed Phase ◽  
Stable Equilibrium ◽  
Constant Pressure ◽  
Saturation Pressure ◽  
Stable State ◽  
Actual State ◽  
Stable States ◽  
Bottom Line ◽  
Thermodynamic Potentials

The thermodynamics of nucleation of a pure vapour is investigated under different constraints. The well-known cases isothermal-isobaric, isothermal-isochoric and isolated are considered. The systems are composed of a number of clusters having identical size. The appropriate thermodynamic potentials are calculated from a common point of view. The actual state of the system, clusters and vapour, is compared to the initial supersaturated state. A very large number of such actual states exist if the amount of molecules in the system is large. They form a surface of the potential function. It is looked for relatively stable states of the system compared to neighbouring states of the system. These states are determined by partial derivation of the potential functions or the determination of gradient curves on the surfaces. In all three cases investigated critical states can be found. They belong to maxima of the potential function in the isothermal-isobaric and the isothermal-isochoric cases and to minima in the isolated case. No stable state can be found in the isothermal-isobaric system. On the contrary in the remaining two cases the stable equilibrium of the bulk condensed phase at saturation pressure can be reached by the system. In the isothermal-isobaric and in the isothermal-isochoric system there exists a bottom line of the potential function surface and in the isolated case a crest line can be found. Both these curves belong to relatively stable states of the system. Nucleation and ripening phases of the system may be attributed to these graphs. It is shown that the Kelvin equation gives a proper description of critical or stable states only in special regions of cluster size and cluster concentrations. It is furthermore demonstrated that the constraint of constant pressure is responsible for the significant differences between the isothermal-isobaric case and the remaining two cases in a one component system. If the presence of an inert substance is allowed the stable equilibrium of the condensed phase at saturation vapour pressure may also be attainable under constant pressure. The considerations presented for the transition vapour condensed phase can easily be applied to phase transitions in condensed phases, respectively.

Study on Bi-Stable Behaviors of Isotropic Shell Structures and Numerical Simulation

2010 ◽  
Vol 168-170 ◽  
pp. 341-344
Author(s):  
Yao Peng Wu
Keyword(s):  
Numerical Simulation ◽  
Boundary Effect ◽  
Stable Process ◽  
Stable State ◽  
Shell Element ◽  
Stable Model ◽  
Stable States ◽  
Isotropic Shell ◽  
Abaqus Code ◽  
Two Parameters

Bi-stable structure can be stable in both its extended and coiled forms. For the elastic isotropic shell, a theoretical model in terms of only two parameters is proposed. Based on the principle of minimum potential energy, the conditions for bi-stability of isotropic shell are derived. The results indicate that, a pre-stressed shell will have its two stable states if the acting pre-stress satisfies some confined conditions. Further, the bi-stable model is improved taking into account boundary effect of the shell. The results show the rolled-up radius for the second stable state becomes larger. Meanwhile, using shell element in ABAQUS code, numerical simulation on bi-stable process is carried out. The numerical results of rolled-up radius characterizing the bi-stability agree well with the predicted results.

scholarly journals ENVIRONMENTAL MANAGEMENT AND AQUATIC ECOLOGY IN SEARCH OF ANSWERS TO THE CHALLENGES OF THE TIME

Ekosistemy ◽  
2021 ◽  
pp. 30-40
Author(s):  
N. V. Shadrin ◽  
E. V. Anufriieva
Keyword(s):  
Environmental Management ◽  
Stable State ◽  
Theoretical Concept ◽  
Natural Ecosystems ◽  
Stable States ◽  
The North ◽  
Ecological Concepts ◽  
The Crimea ◽  
Adaptive Environmental Management ◽  
Rapid Transformation

Currently, the destruction of landscapes is taking place with a decrease in the sustainability and productivity of natural ecosystems. One of the main reasons for this is inadequate environmental management, which, as a rule, is based on inadequate outdated theoretical ecological concepts. The totality of accumulated data shows that real ecosystems can be in several alternative states and demonstrate relatively rapid changes in the regime of existence with significant, abrupt and permanent changes in structure and functioning. In this regard, the main ecosystem paradigm is currently being revised. From the theoretical concept of the unicity of the ecosystem stable state, ecology moves to the concept of the multiplicity of stable states in the ecosystem. The dynamics of ecosystems can be represented, according to K. Holling, in the form of an adaptation cycle with the alternation of four phases, the features of which are considered. The importance of no return points and possible uncertainty in the dynamics of ecosystems are shown. Ecosystems, in a certain sense, have memory, which is the reason for the hysteresis effect during multidirectional changes in systems. The necessity of developing approaches of adaptive ecosystem management based on this concept is shown. Which is especially important in cases of rapid transformation of natural ecosystems, such, as an example, in the Crimea after the cessation of the supply of Dnieper water to the North Crimean canal. The difficulties of transition to adaptive environmental management in modern conditions are analyzed.

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