Search results for "Dynamic system"
showing 10 items of 38 documents
Basic Notions of the Theory of Heat
2016
This chapter summarizes some basic notions of thermodynamics and defines the empirical variables which are needed for the description of thermodynamic systems in equilibrium. Empirical temperature and several scales used to measure temperature are defined. The so-called “zeroth law of thermodynamics” is formulated which says that systems which are in mutual equilibrium have the same temperature. Thermodynamic ensembles corresponding to different macroscopic boundary conditions are introduced and are illustrated by simple models such as the ideal gas. Also, entropy appears on the scene for a first time, both in its statistical and its thermodynamical interpretation. Gibb’s fundamental form i…
Symbolic control for underactuated differentially flat systems
2006
In this paper we address the problem of generating input plans to steer complex dynamical systems in an obstacle-free environment. Plans considered admit a finite description length and are constructed by words on an alphabet of input symbols, which could be e.g. transmitted through a limited capacity channel to a remote system, where they can be decoded in suitable control actions. We show that, by suitable choice of the control encoding, finite plans can be efficiently built for a wide class of dynamical systems, computing arbitrarily close approximations of a desired equilibrium in polynomial time. Moreover, we illustrate by simulations the power of the proposed method, solving the steer…
Stochastic linearization critically re-examined
1997
Abstract The stochastic linearization technique, widely used for the analysis of nonlinear dynamic systems subjected to random excitations, is revisited. It is shown that the standard procedure universally adopted for determining the so-called effective stiffness of the equivalent linear system is erroneous in all previous publications. Two error-free stochastic linearization techniques are elucidated, namely those based on (1) the force linearization and (2) energy linearization.
The frequent stressor and mental health monitoring-paradigm: a proposal for the operationalization and measurement of resilience and the identificati…
2021
Resilience has been defined as the maintenance or quick recovery of mental health during and after times of adversity. How to operationalize resilience and to determine the factors and processes that lead to good long-term mental health outcomes in stressor-exposed individuals is a matter of ongoing debate and of critical importance for the advancement of the field. One of the biggest challenges for implementing an outcome-based definition of resilience in longitudinal observational study designs lies in the fact that real-life adversity is usually unpredictable and that its substantial qualitative as well as temporal variability between subjects often precludes defining circumscribed time …
Moving toward a Supetheory for All Seasons : Dialectical Dynamic Systems Theory and Sociocultural Theory - A Reply to McCafferty (2016)
2016
Moving toward a Supertheory for All Seasons: Dialectical Dynamic Systems Theory and Sociocultural Theory – A Reply to McCafferty (2016)
A Dialectical Reading of Dynamic Systems Theory : Transcending Socialized Cognition and Cognized Social Dualism in L2 Studies
2016
Dynamic systems theory (DST) has affordances to be a quintessential metatheoretical architecture for the nuancing of the time-locked mechanisms and processes of the L2 system. The received construal of DST in L2 studies presumes the emergence of structural regularities and the cognitive organization of the L2 system as simply a function of lower-level language use in social milieux. Critiquing some of the bedrock assumptions anchoring the extant reading, this article sketches a complementary dialectical construal of DST. Explicating circular causality, a nexus of causality types, and self-organizational emergence and their attendant implications for an adequate description and explanation o…
Steering dynamical systems with finite plans and limited path length
2007
Complex dynamical systems can be steered by using symbolic input plans. These plans must have a finite descriptive length, and can be expressed by means of words chosen in an alphabet of symbols. In this way, such plans can be sent through a limited capacity channel to a remote system, where they are decoded in suitable control actions. The choice of this symbols is essential to efficiently encode steering plans. To this aim, in this paper, we state the problem of finding symbols maximizing the interval of points reachable by the system along paths with constrained length. We focus on the problem with two symbols, and compare the results with those produced by plans not accounting for the l…
On basins of attraction for a predator-prey model via meshless approximation
2016
Abstract. In this work an epidemiological predator-prey model is studied. It analyzes the spread of an infectious disease with frequency-dependent and vertical transmission within the predator population. In particular we consider social predators, i.e. they cooperate in groups to hunt. The result is a three-dimensional system in which the predator population is divided into susceptible and infected individuals. Studying the dynamical system and bifurcation diagrams, a scenario was identified in which the model shows multistability but the domain of attraction of one equilibrium point can be so small that it is almost the point itself. From a biological point of view it is important to anal…
Valuing Variability: Dynamic Usage-based Principles in the L2 Development of Four Finnish Language Learners
2020
The general aim of this study is to trace the second language (L2) development of four beginner learners of Finnish over one academic year from a dynamic usage-based perspective. Contrary to many previous studies, this study starts out from meanings, not forms. In other words, an onomasiological approach is adopted. The aim is to investigate what kind of constructions the learners use to express 1) evaluation and 2) existentiality. In line with a dynamic usage-based approach, the goal is to investigate three aspects of development: 1) the interaction between different linguistic means used to express a certain meaning and between the instruction and learning trajectories, 2) variability pat…
Thermodynamics of a Phase-Driven Proximity Josephson Junction
2019
We study the thermodynamic properties of a superconductor/normal metal/superconductor Josephson junction {in the short limit}. Owing to the proximity effect, such a junction constitutes a thermodynamic system where {phase difference}, supercurrent, temperature and entropy are thermodynamical variables connected by equations of state. These allow conceiving quasi-static processes that we characterize in terms of heat and work exchanged. Finally, we combine such processes to construct a Josephson-based Otto and Stirling cycles. We study the related performance in both engine and refrigerator operating mode.