An optimal management strategy for stochastic population dynamics of released Plecoglossus altivelis in rivers

2017 ◽  
Vol 08 (02) ◽  
pp. 1750039 ◽  
Author(s):  
Yuta Yaegashi ◽  
Hidekazu Yoshioka ◽  
Koichi Unami ◽  
Masayuki Fujihara
Keyword(s):  
Mathematical Model ◽  
Population Dynamics ◽  
Management Strategy ◽  
Predation Pressure ◽  
Death Process ◽  
Model Parameters ◽  
Optimal Management ◽  
Plecoglossus Altivelis ◽  
Severe Problem ◽  
Fishery Cooperatives

Excessive predation pressure from the waterfowl Phalacrocorax carbo (Great Cormorant) on Plecoglossus altivelis (Ayu) has recently been a severe problem of river environment in Japan. Local fishery cooperatives are currently suffering from economic difficulties due to decrease of the fish catch of P. altivelis. Local fishery cooperatives and municipalities have been enthusiastically trying to develop countermeasures that can effectively reduce the predation pressure; however, their effectiveness and efficiency have not been systematically quantified well. This aim can be achieved with the help of an appropriate mathematical model. In this paper, based on a pure death process, a practical stochastic control model for population dynamics of released P. altivelis in river environment under predation pressure from P. carbo, harvesting by human, and environmental fluctuations is proposed. Finding an optimal management strategy ultimately reduces to solving a 2D Hamilton–Jacobi–Bellman equation, which is performed with a finite element scheme. Its application to a Japanese river environment successfully computes the optimal management strategy that is consistent with the reality. Numerical sensitivity analysis of the presented mathematical model is also performed for comprehension of dependence of the optimal strategy on the model parameters.

scholarly journals Integrating Systemic Therapies into the Multimodality Treatment of Resectable Colorectal Liver Metastases

2018 ◽  
Vol 2018 ◽  
pp. 1-4 ◽  
Author(s):  
Omar Abdel-Rahman ◽  
Winson Y. Cheung
Keyword(s):  
Liver Metastases ◽  
Management Strategy ◽  
Multimodality Treatment ◽  
Treatment Modalities ◽  
Considerable Proportion ◽  
Optimal Management ◽  
Related Factors ◽  
Multiple Treatment ◽  
Current Review ◽  
Systemic Therapies

Colorectal carcinoma (CRC) is one of the most common cancers worldwide. A considerable proportion of CRC patients may present with metastatic disease either at upfront presentation (synchronous with the primary) or following diagnosis and treatment of the primary tumor (metachronous). Management of CRC liver metastases is a challenging endeavor which frequently necessitates proper assessment of patient- and disease-related factors. There is an opportunity within the management of CRC liver metastases to incorporate multiple treatment modalities (including surgery, other locoregional treatments, and systemic therapy). The current review aims to provide an updated overview on the optimal management strategy for CRC patients with liver metastases with a specific focus on the integration of systemic and/or locoregional treatments among patients with resectable or potentially resectable disease.

scholarly journals A mathematical model of the population dynamics of disease-transmitting vectors with spatial consideration

2011 ◽  
Vol 5 (4) ◽  
pp. 335-365 ◽  
Author(s):  
Siewe Nourridine ◽  
Miranda I. Teboh-Ewungkem ◽  
Gideon A. Ngwa
Keyword(s):  
Mathematical Model ◽  
Population Dynamics

scholarly journals The identification of a device based on a Peltier element by the least squares method

2020 ◽  
pp. 17-27
Author(s):  
Vladimir Grinkevich ◽  
Keyword(s):  
Mathematical Model ◽  
Least Squares ◽  
Least Squares Method ◽  
Control Object ◽  
Object Identification ◽  
Model Parameters ◽  
Peltier Element ◽  
Transport Delay ◽  
Non Linear ◽  
The Mathematical Model

The evaluation of the mathematical model parameters of a non-linear object with a transport delay is considered in this paper. A temperature controlled stage based on a Peltier element is an identification object in the paper. Several input signal implementations are applied to the input of the identification object. The least squares method is applied for the calculation of the non-linear differential equitation parameters which describe the identification object. The least squares method is used due to its simplicity and the possibility of identification non-linear objects. The parameters values obtained in the process of identification are provided. The plots of temperature changes in the temperature control system with a controller designed based on the mathematical model of the control object obtained as a result of identification are shown. It is found that the mathematical model obtained in the process of identification may be applied to design controllers for non-linear systems, in particular for a temperature stage based on a Peltier element, and for self-tuning controllers. However, the least square method proposed in the paper cannot estimate the transport delay time. Therefore it is required to evaluate the time delay by temperature transient processes. Dynamic object identification is applied when it is required to obtain a mathematical model structure and evaluate the parameters by an input and output control object signal. Also, identification is applied for auto tuning of controllers. A mathematical model of a control object is required to design the controller which is used to provide the required accuracy and stability of control systems. Peltier elements are applied to design low-power and small- size temperature stage . Hot benches based on a Peltier element can provide the desired temperature above and below ambient temperature.

scholarly journals How host phenology impacts multi-season epidemic cycles

2021 ◽  
Author(s):  
Hannelore MacDonald ◽  
Dustin Brisson
Keyword(s):  
Mathematical Model ◽  
Population Dynamics ◽  
Population Cycles ◽  
Seasonal Activity ◽  
Host Interactions ◽  
Host Phenology ◽  
Demographic Impact ◽  
Host Parasite ◽  
Parasite Populations ◽  
Parasite Dynamics

Parasite-host interactions can result in periodic population dynamics when parasites over-exploit host populations. The timing of host seasonal activity, or host phenology, determines the frequency and demographic impact of parasite-host interactions which may govern if the parasite can sufficiently over-exploit their hosts to drive population cycles. We describe a mathematical model of a monocyclic, obligate-killer parasite system with seasonal host activity to investigate the consequences of host phenology on host-parasite dynamics. The results suggest that parasites can reach the densities necessary to destabilize host dynamics and drive cycling in only some phenological scenarios, such as environments with short seasons and synchronous host emergence. Further, only parasite lineages that are sufficiently adapted to phenological scenarios with short seasons and synchronous host emergence can achieve the densities necessary to over-exploit hosts and produce population cycles. Host-parasite cycles can also generate an eco-evolutionary feedback that slows parasite adaptation to the phenological environment as rare advantageous phenotypes are driven to extinction when introduced in phases of the cycle where host populations are small and parasite populations are large. The results demonstrate that seasonal environments can drive population cycling in a restricted set of phenological patterns and provides further evidence that the rate of adaptive evolution depends on underlying ecological dynamics.

scholarly journals Industry pollution structure and the optimal management strategy in lower reaches of Lake Qiandao Basin

2017 ◽  
Vol 29 (2) ◽  
pp. 317-325
Author(s):  
LU Wenyan ◽  
◽  
LI Hengpeng ◽  
WU Zhixu ◽  
YU Xingxiu ◽  
...  
Keyword(s):  
Management Strategy ◽  
Optimal Management

scholarly journals A mathematical model of common-cold epidemics on Tristan da Cunha

1971 ◽  
Vol 69 (3) ◽  
pp. 423-433 ◽  
Author(s):  
B. J. Hammond ◽  
D. A. J. Tyrrell
Keyword(s):  
Mathematical Model ◽  
Common Cold ◽  
Average Duration ◽  
Model Parameters ◽  
Epidemic Threshold ◽  
Tristan Da Cunha ◽  
Simulation Techniques ◽  
Time Courses ◽  
The Mathematical Model ◽  
Computer Simulation Techniques

SUMMARYRecords of seven common-cold outbreaks on the island of Tristan da Cunha are compared with the corresponding time courses given by the mathematical model of Kermack & McKendrick (1927) and with an alternative model that directly involves a constant average duration of individual infection. Using computer simulation techniques the latter model is shown to be preferred and is then closely matched to the field data to obtain values for the model parameters. Consideration is then given to the intensity of epidemics predicted by the model and to the distribution of the actual epidemics relative to the theoretical epidemic threshold.

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