共查询到19条相似文献,搜索用时 93 毫秒
1.
2.
3.
本文讨论了一类具有质体非均匀恒化器模型解的持续性,首先利用上下解方法与极值原理得到恒化器模型的先验估计;然后利用非线性系统的持续性理论讨论恒化器模型正解的长时行为,并且得到了当模型中的参数满足特定条件时,该模型对应的半动力系统是强一致连续持续的. 相似文献
4.
5.
本文研究一类Caputo型分数阶SIR传染病模型的全局稳定性.首先,通过对方程进行求解得到了模型的平衡点.然后,根据关于Caputo型分数阶微积分的一个引理和分数阶动力系统的相关理论,分别构造相应的Lyapunov函数判断平衡点的稳定性.结果表明,当R_01时,模型有唯一的无病平衡点E_0,E_0是全局稳定的;如果R_01时,模型存在无病平衡点E_0和地方病平衡点E_*,E_*是全局稳定的.最后,给出了一些数值模拟来验证理论分析的结果. 相似文献
6.
7.
一类具年龄结构的线性周期种群动力系统的最优控制 总被引:1,自引:0,他引:1
研究一类具有年龄结构的线性周期种群线性动力系统的最优控制问题,即讨论了具有周期的生死率和周期变化的控制项的模型.利用Mazur's定理,证明了最优控制问题最优解的存在性,同时由法锥概念的特征刻画,我们还得到了最优控制问题最优解存在的必要条件. 相似文献
8.
9.
建立了具脉冲出生和脉冲收获的基因突变单种群动力学模型.利用离散动力系统的频闪映射理论,得到了生物资源管理控制阈值的充分条件. 相似文献
10.
11.
In the present paper we have first introduced a measure of dynamical entropy of an ecosystem on the basis of the dynamical model of the system. The dynamical entropy which depends on the eigenvalues of the community matrix of the system leads to a consistent measure of complexity of the ecosystem to characterize the dynamical behaviours such as the stability, instability and periodicity around the stationary states of the system. We have illustrated the theory with some model ecosystems. 相似文献
12.
Summary Continuous and semi-continuous flow bioreactors have been developed for the production of chloroperoxidase, which is secreted by the fungusCaldariomyces fumago. The semi-continuous system facilitated the harvest of mycelium-free supernatant for 200 days from a single inoculum, with enzyme levels greater than 600 mg/l during the first 80 days. The continuous flow bioreactor yielded essentially pure enzyme at the rate of 117 mg/day. 相似文献
13.
14.
Taira Hidaka Hiroshi Tsuno Haruka Yagi Yusuke Kosaka 《Biotechnology and Bioprocess Engineering》2012,17(2):290-297
Batch and semi-continuous thermophilic l-lactate fermentation experiments were performed using Bacillus coagulans and glucose as a substrate. Reactor performance and biomass concentrations were assessed using two methods: turbidity as
a traditional biomass index and real-time polymerase chain reaction (PCR) quantification of 16S rRNA genes. In the batch experiment,
although the relationship between turbidity and real-time PCR assay differed depending on the growth phase, a correlation
was observed between both assay methods. In the semi-continuous experiment, real-time PCR measurement was well suited for
use as an index for evaluating bacterial mass under different organic loading conditions. A mathematical model was applied
to evaluate the real-time PCR quantification to long-term, semi-continuous lactate fermentation. Lactate fermentation was
well suited since only B. coagulans was involved in the reactions. The results obtained revealed a fundamental relationship between real-time PCR and traditional
biomass analyses. 相似文献
15.
Giulia Benvenuti Rouke Bosma Fang Ji Packo Lamers Maria J. Barbosa René H. Wijffels 《Journal of applied phycology》2016,28(6):3167-3177
Microalgal triglycerides (TAGs) represent a sustainable feedstock for food, chemical and biofuel industries. The operational strategy (batch, semi-continuous, continuous cultivations) has an impact on the TAG productivity. In this study, semi-continuous (i.e. with fixed harvesting frequency) and batch cultivations were compared on TAG production both at lab-scale and in outdoor cultivations. At lab-scale, the semi-continuous TAG productivity was highest for a cycle time of 2 days (SC1; 0.21 g L?1 day?1) and similar to the maximum obtained with the batch (optimal harvest time; 0.23 g L?1 day?1). Although TAG content was lower for SC1 (22 %) than for the batch (35 %), higher biomass productivities were obtained with SC1. Outdoors, semi-continuous cultivations were subjected to a lower degree of stress (i.e. higher amount of nitrogen present in the system relative to the given irradiance) compared to lab-scale. This yielded low and similar TAG contents (10–13 %) in the different semi-continuous runs that were outdone by the batch on both TAG content (15–25 %) and productivity (batch, 0.97–2.46 g m?2 day?1; semi-continuous, 0.35–0.85 g m?2 day?1). The lab-scale experiments showed that semi-continuous strategies, besides leading to similar TAG productivities compared to the batch, could make TAG production cost effective by valorising also non-TAG compounds. However, optimization of outdoor semi-continuous cultivations is still required. For instance, the nitrogen supply and the harvest frequency should be adjusted on the total irradiance. Additionally, future research should focus on recovery metabolism upon nitrogen resupply. 相似文献
16.
Pan K 《PloS one》2011,6(8):e23910
Original antigenic sin is the phenomenon in which prior exposure to an antigen leads to a subsequent suboptimal immune response to a related antigen. Immune memory normally allows for an improved and rapid response to antigens previously seen and is the mechanism by which vaccination works. I here develop a dynamical system model of the mechanism of original antigenic sin in influenza, clarifying and explaining the detailed spin-glass treatment of original antigenic sin. The dynamical system describes the viral load, the quantities of healthy and infected epithelial cells, the concentrations of naïve and memory antibodies, and the affinities of naïve and memory antibodies. I give explicit correspondences between the microscopic variables of the spin-glass model and those of the present dynamical system model. The dynamical system model reproduces the phenomenon of original antigenic sin and describes how a competition between different types of B cells compromises the overall effect of immune response. I illustrate the competition between the naïve and the memory antibodies as a function of the antigenic distance between the initial and subsequent antigens. The suboptimal immune response caused by original antigenic sin is observed when the host is exposed to an antigen which has intermediate antigenic distance to a second antigen previously recognized by the host''s immune system. 相似文献
17.
We consider a stage-structured model of a harvested fish population and we are interested in the problem of estimating the
unknown stock state for each class. The model used in this work to describe the dynamical evolution of the population is a
discrete time system including a nonlinear recruitment relationship. To estimate the stock state, we build an observer for
the considered fish model. This observer is an auxiliary dynamical system that uses the catch data over each time interval
and gives a dynamical estimate of the stock state for each stage class. The observer works well even if the recruitment function
in the considered model is not well known. The same problem for an age-structured model has been addressed in a previous work
(Ngom et al., Math. Biosci. Eng. 5(2):337–354, 2008). 相似文献
18.
Summary The insect cell - baculovirus system is used to synthesize a variety of recombinant proteins, generally in a batch system. We have developed a semi-continuous system and studied its operation at three different residence times. The resulting data showed that beta-galactosidase can be produced for 50 to 150 hours longer than the batch system. 相似文献