scholarly journals Investigating cholera using an SIR model with age-class structure and optimal control

2016 ◽  
Vol 9 (1) ◽  
pp. 83-100 ◽  
Author(s):  
K. Renee Fister ◽  
Holly Gaff ◽  
Elsa Schaefer ◽  
Glenna Buford ◽  
Bryce Norris
Keyword(s):  
Optimal Control ◽  
Sir Model ◽  
Class Structure ◽  
Age Class

A stochastic characterisation of the natural disturbance regime of the boreal mixedwood forest with implications for sustainable forest management

1999 ◽  
Vol 29 (4) ◽  
pp. 424-433 ◽  
Author(s):  
Glen W Armstrong
Keyword(s):  
Monte Carlo ◽  
Sustainable Forest Management ◽  
Natural Disturbance ◽  
Class Structure ◽  
Distribution Models ◽  
Age Class ◽  
Boreal Mixedwood Forest ◽  
Random Draw ◽  
Negative Exponential ◽  
Burn Rate

The annual area burned on an 8.6 × 106 ha study area in the boreal mixedwood forest of northeastern Alberta, Canada, was characterised as a serially independent random draw from a lognormal distribution. This characterisation was applied in Monte Carlo simulations, which showed that estimates of the mean annual burn rates, even with long sample periods, are highly imprecise. Monte Carlo simulation was also used to simulate the development of a forest subject to lognormally distributed annual burn rate in an attempt to characterise the equilibrium age-class structure. No equilibrium age-class structure could be identified from the simulation results. The validity of equilibrium age-class distribution models (e.g., the negative exponential and Weibull) and analysis that relies on these models is questioned for forests where the annual burn rate is highly variable.

scholarly journals Dynamic analysis and optimal control of a three-age-class HIV/AIDS epidemic model in China

2020 ◽  
Vol 25 (9) ◽  
pp. 3491-3521
Author(s):  
Hongyong Zhao ◽  
◽  
Peng Wu ◽  
Shigui Ruan ◽  
Keyword(s):  
Optimal Control ◽  
Dynamic Analysis ◽  
Epidemic Model ◽  
Age Class ◽  
Aids Epidemic ◽  
Hiv Aids

Influence of Swiss needle cast on foliage age-class structure and vertical foliage distribution in Douglas-fir plantations in north coastal Oregon

2006 ◽  
Vol 36 (6) ◽  
pp. 1497-1508 ◽  
Author(s):  
Aaron R Weiskittel ◽  
Douglas A Maguire ◽  
Sean M Garber ◽  
Alan Kanaskie
Keyword(s):  
Vertical Distribution ◽  
Douglas Fir ◽  
Parameter Estimates ◽  
Class Structure ◽  
Needle Cast ◽  
Age Class ◽  
Relative Contribution ◽  
Crown Structure ◽  
Growth Decline ◽  
Swiss Needle Cast

Swiss needle cast (SNC) causes premature loss of foliage and subsequent growth decline in Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco). Although the mechanisms leading to this growth decline include loss of photosynthetic surface area and physiological disruption of surviving foliage, estimating the relative contribution of these two primary sources requires precise quantification of SNC effects on total foliage mass, foliage age-class structure, and vertical foliage distribution. The effect of SNC severity on these crown structural attributes was tested across a range of stand densities and site qualities in 10- to 60-year-old plantations in north coastal Oregon. Foliage mass in each age-class was sampled at the branch level, and the resulting equations were applied to all live branches on intensively measured sample trees. Vertical distribution of each foliage age-class was described by a beta distribution fitted to each sample tree, and sources of variation in vertical distribution were tested by regressing beta parameter estimates on SNC intensity and other covariates representing tree, stand, and site attributes. Distribution of foliage mass by age-class and by relative height in the crown was significantly affected by SNC severity, in addition to other covariates such as crown size and tree social position. SNC caused a reduction in the amount of foliage in each age-class and greater relative representation of younger needles. SNC also shifted the mode of relative vertical distribution toward the top of the tree for the three youngest foliage age-classes, but toward the base of the crown for 4- and 5-year-old foliage. Quantification of foliage age-class structure and vertical distribution across a range of SNC severity has helped to establish diagnostic criteria for assessing changes in crown structure that precede declines in growth and vigor. The induced changes in crown structure will also help to identify the relative contribution of several mechanisms causing growth losses in diseased trees.

scholarly journals Economic impacts of partial harvesting: Mitigating mid-term timber supply shortages as a result of pest outbreaks

2021 ◽  
Vol 97 (3) ◽  
pp. 271-276
Author(s):  
Torben Jensen ◽  
Jean-Martin Lussier
Keyword(s):  
Class Structure ◽  
Forest Sector ◽  
Timber Supply ◽  
Age Class ◽  
Eastern Spruce Budworm ◽  
Partial Harvesting ◽  
Pest Outbreaks ◽  
Supply Analysis ◽  
Regional Forest ◽  
Mature Stands

Natural disturbances such as pest outbreaks have a significant impact on forest dynamics and services, including the loss of mature stands. From a wood production perspective, these disturbances can lead to long-lasting imbalances in the overall age-class structure of the forest, potentially resulting in a shortage of mature harvestable stands. Researchers from Natural Resources Canada’s (NRCan) Canadian Forest Service (CFS) have made a timber supply analysis of the Dunière forest located in the centre of the Gaspé Peninsula (Québec). This region suffers from an age-class structure imbalance caused by an eastern spruce budworm (ESB) outbreak that ended in 1984, and is consequently facing a reduced annual allowable cut, leading to long- term implications for the regional forest sector. The authors suggest that partial harvesting – the removal of a proportion of timber in a mature stand several years before a final cut is carried out – is a promising opportunity in the ESB-affected area for mitigating mid-term timber supply shortages by smoothing the fibre supply over time.

scholarly journals A Survey on Two Viruses Extensions of Epidemic Model with Continuous and Impulse Control

2021 ◽  
Vol 14 ◽  
pp. 127-154
Author(s):  
Elena Gubar ◽  
◽  
Vladislav Taynitskiy ◽  
Keyword(s):  
Optimal Control ◽  
Optimal Control Problem ◽  
Network Structure ◽  
Epidemic Model ◽  
Impulse Control ◽  
Sir Model ◽  
Initial Population ◽  
Protection Measures ◽  
Virus Spreading ◽  
Theoretical Results

The current study represents a survey on several modifications of compartment epidemic models with continuous and impulse control policies. The main contribution of the survey is the modification of the classical Susceptible Infected Recovered (SIR) model with the assumption that two types of viruses are circulating in the population at the same time. Moreover, we also take into consideration the network structure of the initial population in two-virus SIIR models and estimate the e ectiveness of protection measures over complex networks. In each model, the optimal control problem has been formalized to minimize the costs of the virus spreading and find optimal continuous and impulse antivirus controllers. All theoretical results are corroborated by a large number of numerical simulations.

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