periodic dynamics
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2021 ◽  
Author(s):  
Simon Victory Quarcson Hamenoo ◽  
Rudith King ◽  
Theresa Yaaba Baah-Ennumh ◽  
Jennifer Dokbila Mengba ◽  
Stephen Boadi Gyamfi

Abstract This study was designed to assess reading difficulty dynamics and develop the corresponding interventions for students in the Banka Community Senior High School within the Asante Akyem South Municipality of Ghana. The study used multiple research designs and research methods in soliciting data for the analysis. Both semi-structured questionnaires and interview guides were used for data collection. A 100-worded paragraph was taken from the introductory page of the Integrated Science Textbook for Senior High Schools to assess the reading difficulty of students using the One-Minute Administration of Reading Passages (OARP) protocol. Three sessions of readings were done; the first without intervention, and the subsequent readings with teacher interventions. The results of the study show that majority of the respondents had text recognition accuracy (TRA), text pronunciation accuracy (TPA) and reading speed (RS) problems. Thus, TRA, TPA, and RS scores were below the 80% benchmark in the first reading (without intervention). Nevertheless, TRA, TPA, and RS scores increased above the 80% benchmark for the second and third readings (with teacher interventions). Four causative factors for the reading difficulties (RDs), three locational dynamics, four durational dynamics, four reading frequency dynamics and four periodic dynamics of RDs were identified. The study concludes that RD reduces with teacher interventions. The findings of this study is not a generalization of reading difficulty dynamics and intervention in all community schools in Ghana but rather presents contributions to an emerging academic problem which could have implications on SDG 4 in the near future within community schools. Hence, the need for setting up reading clubs in community schools towards reducing reading difficulties among students.


2021 ◽  
Vol 104 (5) ◽  
Author(s):  
Frederic Folz ◽  
Kurt Mehlhorn ◽  
Giovanna Morigi

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Deeptajyoti Sen ◽  
Sudeshna Sinha

AbstractWe consider the dynamics of a three-species system incorporating the Allee Effect, focussing on its influence on the emergence of extreme events in the system. First we find that under Allee effect the regular periodic dynamics changes to chaotic. Further, we find that the system exhibits unbounded growth in the vegetation population after a critical value of the Allee parameter. The most significant finding is the observation of a critical Allee parameter beyond which the probability of obtaining extreme events becomes non-zero for all three population densities. Though the emergence of extreme events in the predator population is not affected much by the Allee effect, the prey population shows a sharp increase in the probability of obtaining extreme events after a threshold value of the Allee parameter, and the vegetation population also yields extreme events for sufficiently strong Allee effect. Lastly we consider the influence of additive noise on extreme events. First, we find that noise tames the unbounded vegetation growth induced by Allee effect. More interestingly, we demonstrate that stochasticity drastically diminishes the probability of extreme events in all three populations. In fact for sufficiently high noise, we do not observe any more extreme events in the system. This suggests that noise can mitigate extreme events, and has potentially important bearing on the observability of extreme events in naturally occurring systems.


Energies ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 5069
Author(s):  
Wasim Sarwar ◽  
Fernando Mellibovsky ◽  
Md. Mahbub Alam ◽  
Farhan Zafar

This study focuses on the numerical investigation of the underlying mechanism of transition from chaotic to periodic dynamics of circular cylinder wake under the action of time-dependent fluidic actuation at the Reynolds number = 2000. The forcing is realized by blowing and suction from the slits located at ±90∘ on the top and bottom surfaces of the cylinder. The inverse period-doubling cascade is the underlying physical mechanism underpinning the wake transition from mild chaos to perfectly periodic dynamics in the spanwise-independent, time-dependent forcing at twice the natural vortex-shedding frequency.


2021 ◽  
pp. 2362-2368
Author(s):  
Safaa Jawad Ali ◽  
Abed Almohsen Naji Almohasin ◽  
Adwea Naji Atewi ◽  
Raid Kamel Naji ◽  
Norihan Md Arifin

In this paper, chaotic and periodic dynamics in a hybrid food chain system with Holling type IV and Lotka-Volterra responses are discussed. The system is observed to be dissipative. The global stability of the equilibrium points is analyzed using Routh-Hurwitz criterion and Lyapunov direct method. Chaos phenomena is characterized by attractors and bifurcation diagram. The effect of the controlling parameter of the model is investigated theoretically and numerically.


Author(s):  
Fausto Cavalli ◽  
Ahmad Naimzada ◽  
Lucia Parisio

AbstractIn this paper, we study a class of markets, among which we can mention agricultural and energy markets, characterized by seasonality, i.e., in which demand and/or supply conditions cyclically alternate with a precise and known periodicity. We propose a new theoretical framework based on a cobweb model with adaptive expectations, accordingly modified to be consistent with market’s seasonality. The model, consisting in a second-order non-autonomous difference equation, is investigated with the aim of understanding how the periodical nature of the market together with the agents’ expectation formation mechanism affects the resulting dynamics. We analytically prove the emergence of dynamical scenarios that are missing in the classic cobweb model for non-seasonal markets, such as quasi-periodic dynamics and an ambiguous role on stability of the expectation weight. Finally, we discuss their economic rationale with the help of numerical simulations. In such a peculiar economic framework, agents’ learning plays a key role to explain the dynamical properties of economic observables.


2021 ◽  
pp. 639-657
Author(s):  
Ekhlas Abd Al-Husain Jabr ◽  
Dahlia Khaled Bahlool

This paper aims to study the role of a prey refuge that depends on both prey and predator species on the dynamics of a food web model. It is assumed that the food transfer among the web levels occurs according to Lotka-Volterra functional response. The solution properties, such as existence, uniqueness, and uniform boundedness, are discussed. The local, as well as the global, stabilities of the solution of the system are investigated. The persistence of the system is studied with the assistance of average Lyapunov function. The local bifurcation conditions that may occur near the equilibrium points are established. Finally, numerical simulation is used to confirm our obtained results. It is observed that the system has only one type of attractors that is a stable point, while periodic dynamics do not exist even on the boundary planes.


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