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Environmental Risk Assessment
Published in Sven Erik Jørgensen, A Systems Approach to the Environmental Analysis of Pollution Minimization, 2020
S.E. Jørgensen, Bent Halling Sørensen
Ecotoxicological models in population dynamics. Population models are biode-mographic models and therefore have numbers of individuals or species as state variables. The simple population models consider only one population. The growth of the population is a result of the difference between natality and mortality: dN/dt=B*N-M*N=r*N
Provision of additional food as a tool of biological control in a delayed predator–prey interaction with prey refuge
Published in International Journal of Modelling and Simulation, 2022
Sudeshna Mondal, G. P. Samanta
(2) On the other hand, high quality of additional food enhances the growth rate of predator even after continuous increment of . But at high prey refuge () population dynamics, prey species is going towards its carrying capacity and predator species will survive on provision of high quality of additional food (see Figure 11). In this manner predator species is controlled from extinction. Again, high quality but low quantity of additional food may not help biological conservation in ecosystem in high prey refuge population dynamics (see Figure 12(b)). So, the study of high quality and high quantity of additional food in our proposed model is very significant and biologically consistent for maintaining ecological balance.
Dynamic analysis on a delayed nonlinear density-dependent mortality Nicholson's blowflies model
Published in International Journal of Control, 2021
In Berezansky and Braverman (2017), the authors proposed the following delayed differential equation: to characterise many models in population dynamics. Here m and l are positive integer, and G are nonnegative continuous functions. Moreover, the function is the production incorporating delay, and G describes the instantaneous mortality. Evidently, (1) contains the nonlinear density-dependent mortality Nicholson's blowflies model where are the classical models (Berezansky, Braverman, & Idels, 2010; Liu, Chen, Huang, & Zhou, 2019; Liu, Gong, Teo, & Caccetta, 2017; Wang, 2017; Yao, 2018). Here, corresponds to the death rate of the population, describes the time-dependent birth function which involves maturation delay and incubation delay and gains the reproduces at its maximum rate , all parameter functions of (2) are nonnegative, continuous and bounded, and are bounded below by positive constants, and .
Infrastructure epistemologies: water, wastewater and displaced persons in Germany
Published in Construction Management and Economics, 2018
Population dynamics are a challenge for civil infrastructure. The built assets that comprise the physical components of infrastructure systems are expensive, their design and construction take significant time, and they are sized to serve a particular number of people. While there is certainly some flexibility to the scale of service an asset can provide, significant deviations reduce performance efficiency and sometimes asset longevity (Halpin et al. 2017). For example, if populations grow without a corresponding increase in the wastewater infrastructure that serves them, the environment and public health may be impacted by overflows of raw sewage from treatment plants. In contrast, if populations shrink the fixed operational costs of underutilized infrastructure systems may become excessive on a per capita basis (Faust et al. 2016). Additionally, underutilization may result in changes in performance such as the stagnation of water or increased water age. Fortunately, while population change is a challenge for infrastructure, it typically occurs relatively slowly. For example, between 2011 and 2015, the greater London area was the fastest growing urban region in the UK with an increase of 5.7% of population, with average UK population growth closer to 2.5% across the same timeframe (ONS 2016). In addition, long-range demographic projections mean that this kind of population change is reasonably predictable, enabling advance planning, operational changes, and the time for design and construction that can circumvent many potential issues.