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Stability Analysis of Time-Delayed Linear Fractional-Order Systems
Mohammad Ali Pakzad,Sara Pakzad,Mohammad Ali Nekoui 제어·로봇·시스템학회 2013 International Journal of Control, Automation, and Vol.11 No.3
In this article, an exact and robust method for the determination of all the possible stability regions in the parametric space has been presented for the fractional order systems with time delay. Using the approach presented in this study, first, the transcendental terms have been eliminated from the characteristic equation and then, all the locations on the imaginary axis crossed by the roots and also their direction of crossing have been calculated. Finally, the concept of the stability as a function of the time delay has been described for a general class of linear fractional order systems with several commensurate delays. Prior to the conclusion, several examples have been given to validate the results of the proposed approach.
Saber Soltani,Milad Zandi,Samireh Faramarzi,Ramin Shahbahrami,Mohebat Vali,Sara Akhavan Rezayat,Reza Pakzad,Pooneh Malekifar,Iraj Pakzad,Neda Jahandoost,Jalal Moludi 질병관리본부 2022 Osong Public Health and Research Persptectives Vol.13 No.1
Microbial coinfections can increase the morbidity and mortality rates of viral respiratory diseases. Therefore, this study aimed to determine the pooled prevalence of fungal coinfections in coronavirus disease 2019 (COVID-19) patients. Web of Science, Medline, Scopus, and Embase were searched without language restrictions to identify the related research on COVID-19 patients with fungal coinfections from December 1, 2019, to December 30, 2020. A random-effects model was used for analysis. The sample size included 2,246 patients from 8 studies. The pooled prevalence of fungal coinfections was 12.60%. The frequency of fungal subtype coinfections was 3.71% for Aspergillus, 2.39% for Candida, and 0.39% for other. The World Health Organization’s Regional Office for Europe and Regional Office for Southeast Asia had the highest (23.28%) and lowest (4.53%) estimated prevalence of fungal coinfection, respectively. Our findings showed a high prevalence of fungal coinfections in COVID-19 cases, which is a likely contributor to mortality in COVID-19 patients. Early identification of fungal pathogens in the laboratory for COVID-19 patients can lead to timely treatment and prevention of further damage by this hidden infection.