In gene regulatory networks, gene regulation loops often occur with multiple positive feedback, multiple negative feedback and coupled positive and negative feedback forms. In above gene regulation loops, auto-activat...In gene regulatory networks, gene regulation loops often occur with multiple positive feedback, multiple negative feedback and coupled positive and negative feedback forms. In above gene regulation loops, auto-activation loops are ubiquitous regulatory motifs. This paper aims to investigate a two-component dual-positive feedback genetic circuit, which consists of a double negative feedback circuit and an additional positive feedback loop(APFL). We study effect of substrate concentration on gene expression in the single and the networked systems with APFLs, respectively. We find that substrate concentration can tune stochastic switch behavior in the signal system and then we explore relationship of substrate concentration with positive feedback strength in aspect of stochastic switch behavior. Furthermore, we also discuss gene expression and stochastic switch behavior in the networked systems with APFLs. Based on analysis in the networked systems, we discover that genes express in some specific cells and do not express in the other cells when the expression achieves its steady state. These results can be used to well explain the character of regionalization in the expression of genes and the phenomenon of gene differentiation.展开更多
For pulse-width modulated(PWM)DC-DC converters,the input voltage fluctuation and load variation in practical applications make it necessary for them to have better dynamic performance to meet the regulation requiremen...For pulse-width modulated(PWM)DC-DC converters,the input voltage fluctuation and load variation in practical applications make it necessary for them to have better dynamic performance to meet the regulation requirements of the system.The dynamic-performance-improvement method for PWM DC-DC converters is mainly based on indirect dynamic performance indices,such as the gain margin and phase margin.However,both settling time and overshoot in the time domain are important in practical engineering.This makes it difficult for designers to obtain a clear understanding of the time-domain dynamic performance that can be achieved with improved control.In this study,a direct analysis of the time-domain dynamic characteristic of PWM DC-DC converters is performed.A dynamic-performance-improvement method based on eigenvalues and eigenvector sensitivity(E2S-based DPIM)is proposed to directly improve the time-domain dynamic performance index of PWM DC-DC converters.By considering a boost converter with proportional-integral control as an example,an additional virtual inductor current feedback control was designed using the proposed dynamic-performance-improvement method.Simulation and experimental results verify the validity and accuracy of the proposed dynamic-performance-improvement method.展开更多
基金supported by the National Key Research and Development Program of China(Grant No.2016YFB0800401)the National Natural Science Foundation of China(Grant Nos.61773153,61621003,61532020,11472290,and 61472027)
文摘In gene regulatory networks, gene regulation loops often occur with multiple positive feedback, multiple negative feedback and coupled positive and negative feedback forms. In above gene regulation loops, auto-activation loops are ubiquitous regulatory motifs. This paper aims to investigate a two-component dual-positive feedback genetic circuit, which consists of a double negative feedback circuit and an additional positive feedback loop(APFL). We study effect of substrate concentration on gene expression in the single and the networked systems with APFLs, respectively. We find that substrate concentration can tune stochastic switch behavior in the signal system and then we explore relationship of substrate concentration with positive feedback strength in aspect of stochastic switch behavior. Furthermore, we also discuss gene expression and stochastic switch behavior in the networked systems with APFLs. Based on analysis in the networked systems, we discover that genes express in some specific cells and do not express in the other cells when the expression achieves its steady state. These results can be used to well explain the character of regionalization in the expression of genes and the phenomenon of gene differentiation.
基金Supported by the Key Program of National Natural Science Foundation of China under Grant No.52237008.Digital Object Identifier:10.23919/CJEE.2023.000017。
文摘For pulse-width modulated(PWM)DC-DC converters,the input voltage fluctuation and load variation in practical applications make it necessary for them to have better dynamic performance to meet the regulation requirements of the system.The dynamic-performance-improvement method for PWM DC-DC converters is mainly based on indirect dynamic performance indices,such as the gain margin and phase margin.However,both settling time and overshoot in the time domain are important in practical engineering.This makes it difficult for designers to obtain a clear understanding of the time-domain dynamic performance that can be achieved with improved control.In this study,a direct analysis of the time-domain dynamic characteristic of PWM DC-DC converters is performed.A dynamic-performance-improvement method based on eigenvalues and eigenvector sensitivity(E2S-based DPIM)is proposed to directly improve the time-domain dynamic performance index of PWM DC-DC converters.By considering a boost converter with proportional-integral control as an example,an additional virtual inductor current feedback control was designed using the proposed dynamic-performance-improvement method.Simulation and experimental results verify the validity and accuracy of the proposed dynamic-performance-improvement method.
