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Your search keyword '"The World Academy of Sciences"' showing total 3 results
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3 results on '"The World Academy of Sciences"'

1. Stabilization of periodic orbits near a subcritical Hopf bifurcation in delay-coupled networks

Author

German Academic Exchange Service, German Research Foundation, The World Academy of Sciences, Choe, Chol-Ung, Jang, Hyok, Flunkert, Valentín, Dahms, Thomas, Hövel, Philipp, Schöll, Eckehard, German Academic Exchange Service, German Research Foundation, The World Academy of Sciences, Choe, Chol-Ung, Jang, Hyok, Flunkert, Valentín, Dahms, Thomas, Hövel, Philipp, and Schöll, Eckehard

Abstract

We study networks of delay-coupled oscillators with the aim to extend time-delayed feedback control to networks. We show that unstable periodic orbits of a network can be stabilized by a noninvasive, delayed coupling. We state criteria for stabilizing the orbits by delay-coupling in networks and apply these to the case where the local dynamics is close to a subcritical Hopf bifurcation, which is representative of systems with torsion-free unstable periodic orbits. Using the multiple scale method and the master stability function approach, the network system is reduced to the normal form, and the characteristic equations for Floquet exponents are derived in an analytical form, which reveals the coupling parameters for successful stabilization. Finally, we illustrate the results by numerical simulations of the Lorenz system close to a subcritical Hopf bifurcation. The unstable periodic orbits in this system have no torsion, and hence cannot be stabilized by the conventional time delayed-feedback technique.

Published
2013

2. Stabilization of periodic orbits near a subcritical Hopf bifurcation in delay-coupled networks

Author

Valentin Flunkert, Eckehard Schöll, Thomas Dahms, Philipp Hövel, Hyok Jang, Chol-Ung Choe, German Academic Exchange Service, German Research Foundation, and The World Academy of Sciences

Subjects
Hopf bifurcation, Floquet theory, Delay, General Mathematics, Mathematical analysis, Saddle-node bifurcation, Lorenz system, Bifurcation diagram, Biological applications of bifurcation theory, Stabilization, Computer Science Applications, symbols.namesake, Pitchfork bifurcation, Control theory, Control, symbols, Networks, Master stability function, Mathematics
Abstract

We study networks of delay-coupled oscillators with the aim to extend time-delayed feedback control to networks. We show that unstable periodic orbits of a network can be stabilized by a noninvasive, delayed coupling. We state criteria for stabilizing the orbits by delay-coupling in networks and apply these to the case where the local dynamics is close to a subcritical Hopf bifurcation, which is representative of systems with torsion-free unstable periodic orbits. Using the multiple scale method and the master stability function approach, the network system is reduced to the normal form, and the characteristic equations for Floquet exponents are derived in an analytical form, which reveals the coupling parameters for successful stabilization. Finally, we illustrate the results by numerical simulations of the Lorenz system close to a subcritical Hopf bifurcation. The unstable periodic orbits in this system have no torsion, and hence cannot be stabilized by the conventional time delayed-feedback technique., CUC acknowledges support from TWAS with the code-number 09-138 RG/PHYS/AS_SI. PH acknowledges support by the BMBF under the grant no. 01GQ1001B (Förderkennzeichen). VF and PH acknowledge financial support from the German Academic Exchange Service (DAAD). This work was also supported by DFG in the framework of SFB 910.

Published
2013

3. Using system dynamics modeling approach to strengthen health systems to combat cancer: a systematic literature review.

Author

Chen X, Cai K, Xue Y, Ung COL, Hu H, and Jakovljevic M

Subjects
Humans, Delivery of Health Care organization & administration, Systems Analysis, Palliative Care, Early Detection of Cancer methods, Neoplasms therapy
Abstract

Aim: Dynamic cancer control is a current health system priority, yet methods for achieving it are lacking. This study aims to review the application of system dynamics modeling (SDM) on cancer control and evaluate the research quality., Methods: Articles were searched in PubMed, Web of Science, and Scopus from the inception of the study to 15 November 2023. Inclusion criteria were English original studies focusing on cancer control with SDM methodology, including prevention, early detection, diagnosis and treatment, and palliative care. Exclusion criteria were non-original research, and studies lacking SDM focus. Analysis involved categorization of studies and extraction of relevant data to answer the research question, ensuring a comprehensive synthesis of the field. Quality assessment was used to evaluate the SDM for cancer control., Results: Sixteen studies were included in this systematic review predominantly from the United States (7, 43.75%), with a focus on breast cancer research (5, 31.25%). Studies were categorized by WHO cancer control modules, and some studies may contribute to multiple modules. The results showed that included studies comprised two focused on prevention (1.25%), ten on early detection (62.50%), six on diagnosis and treatment (37.50%), with none addressing palliative care. Seven studies presented a complete SDM process, among which nine developed causal loop diagrams for conceptual models, ten utilized stock-flow charts to develop computational models, and thirteen conducted simulations., Limitations: This review's macrofocus on SDM in cancer control missed detailed methodological analysis. The limited number of studies and lack of stage-specific intervention comparisons limit comprehensiveness. Detailed analysis of SDM construction was also not conducted, potentially overlooking nuances in cancer control strategies., Conclusion: SDM in cancer control is underutilized, focusing mainly on early detection and treatment. Inconsistencies suggest a need for standardized SDM approaches. Future research should expand SDM's application and integrate it into cancer control strategies.

Published
2025
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