scholarly journals The Influence of Temporal Migration in the Synchronization of Populations

2015 ◽  
Vol 16 (1) ◽  
pp. 31
Author(s):  
Vanderlei Manica ◽  
Jacques Aveline Loureiro da Silva
Keyword(s):  
Population Dynamics ◽  
Patch Dynamics ◽  
Metapopulation Model ◽  
Migration Process ◽  
Time Step ◽  
Analytical Criterion ◽  
Local Patch ◽  
And Migration ◽  
The Stability

A discrete metapopulation model with temporal dependent migration is proposed in order to study the stability of synchronized dynamics. During each time step, we assume that there are two processes involved in the population dynamics: local patch dynamics and migration process between the patches that compose the metapopulation. We obtain an analytical criterion that depends on the local patch dynamics (Lyapunov number) and on the whole migration process. The stability of synchronized dynamics depends on how individuals disperse among the patches.

scholarly journals Stability analysis of the coexistence equilibrium of a balanced metapopulation model

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Shodhan Rao ◽  
Nathan Muyinda ◽  
Bernard De Baets
Keyword(s):  
Equilibrium Point ◽  
Mathematical Proof ◽  
Mean Field ◽  
Patch Dynamics ◽  
System Modelling ◽  
Metapopulation Model ◽  
Ode System ◽  
Homogeneous Network ◽  
The Stability ◽  
Coexistence Equilibrium

AbstractWe analyze the stability of a unique coexistence equilibrium point of a system of ordinary differential equations (ODE system) modelling the dynamics of a metapopulation, more specifically, a set of local populations inhabiting discrete habitat patches that are connected to one another through dispersal or migration. We assume that the inter-patch migrations are detailed balanced and that the patches are identical with intra-patch dynamics governed by a mean-field ODE system with a coexistence equilibrium. By making use of an appropriate Lyapunov function coupled with LaSalle’s invariance principle, we are able to show that the coexistence equilibrium point within each patch is locally asymptotically stable if the inter-patch dispersal network is heterogeneous, whereas it is neutrally stable in the case of a homogeneous network. These results provide a mathematical proof confirming the existing numerical simulations and broaden the range of networks for which they are valid.

Labor Markets and Migration

2017 ◽  
Author(s):  
Philip Martin
Keyword(s):  
Labor Markets ◽  
Labor Migration ◽  
Second Phase ◽  
Migration Process ◽  
And Migration ◽  
R Functions

Labor markets have the three R functions of recruiting workers, remunerating them to encourage them to perform their jobs satisfactorily, and retaining experienced and productive workers. Employers in one country and jobs in another complicate these three Rs, especially recruitment, which is why both employers and workers often turn to private recruiters to act as intermediaries between jobs and workers. Recruiters are most deeply involved in the second phase of the four-phase labor migration process—matching workers with jobs. Indeed, the fact that recruiters rarely visit the workplaces to which they send workers, and do not always expect to send more workers to particular employers, reduces their incentives to make good worker–job matches.

scholarly journals On the Numerical Simulation of HPDEs Using θ-Weighted Scheme and the Galerkin Method

Mathematics ◽  
2020 ◽  
Vol 9 (1) ◽  
pp. 78
Author(s):  
Haifa Bin Jebreen ◽  
Fairouz Tchier
Keyword(s):  
Differential Equation ◽  
Galerkin Method ◽  
Linear Ordinary Differential Equation ◽  
Time Interval ◽  
Hyperbolic Partial Differential Equation ◽  
Time Step ◽  
Numerical Examples ◽  
One Dimensional ◽  
The Stability ◽  
The Galerkin Method

Herein, an efficient algorithm is proposed to solve a one-dimensional hyperbolic partial differential equation. To reach an approximate solution, we employ the θ-weighted scheme to discretize the time interval into a finite number of time steps. In each step, we have a linear ordinary differential equation. Applying the Galerkin method based on interpolating scaling functions, we can solve this ODE. Therefore, in each time step, the solution can be found as a continuous function. Stability, consistency, and convergence of the proposed method are investigated. Several numerical examples are devoted to show the accuracy and efficiency of the method and guarantee the validity of the stability, consistency, and convergence analysis.

scholarly journals Modeling the ecology of parasitic plasmids

2021 ◽  
Author(s):  
Jaime G. Lopez ◽  
Mohamed S. Donia ◽  
Ned S. Wingreen
Keyword(s):  
Mathematical Modeling ◽  
Population Dynamics ◽  
Tragedy Of The Commons ◽  
Fitness Costs ◽  
Metapopulation Model ◽  
The Commons ◽  
Modern Biotechnology ◽  
Natural Ecology ◽  
Unique Plasmid ◽  
Competing Populations

AbstractPlasmids are autonomous genetic elements that can be exchanged between microorganisms via horizontal gene transfer (HGT). Despite the central role they play in antibiotic resistance and modern biotechnology, our understanding of plasmids’ natural ecology is limited. Recent experiments have shown that plasmids can spread even when they are a burden to the cell, suggesting that natural plasmids may exist as parasites. Here, we use mathematical modeling to explore the ecology of such parasitic plasmids. We first develop models of single plasmids and find that a plasmid’s population dynamics and optimal infection strategy are strongly determined by the plasmid’s HGT mechanism. We then analyze models of co-infecting plasmids and show that parasitic plasmids are prone to a “tragedy of the commons” in which runaway plasmid invasion severely reduces host fitness. We propose that this tragedy of the commons is averted by selection between competing populations and demonstrate this effect in a metapopulation model. We derive predicted distributions of unique plasmid types in genomes—comparison to the distribution of plasmids in a collection of 17,725 genomes supports a model of parasitic plasmids with positive plasmid–plasmid interactions that ameliorate plasmid fitness costs or promote the invasion of new plasmids.

scholarly journals The influence of density in population dynamics with strong and weak Allee effect

2021 ◽  
Vol 29 (1) ◽  
Author(s):  
Kamrun Nahar Keya ◽  
Md. Kamrujjaman ◽  
Md. Shafiqul Islam
Keyword(s):  
Population Dynamics ◽  
Allee Effect ◽  
Global Bifurcation ◽  
Reaction Diffusion ◽  
Logistic Growth ◽  
Allee Effects ◽  
Reaction Diffusion Model ◽  
Positive Steady States ◽  
The Stability ◽  
The Impact

AbstractIn this paper, we consider a reaction–diffusion model in population dynamics and study the impact of different types of Allee effects with logistic growth in the heterogeneous closed region. For strong Allee effects, usually, species unconditionally die out and an extinction-survival situation occurs when the effect is weak according to the resource and sparse functions. In particular, we study the impact of the multiplicative Allee effect in classical diffusion when the sparsity is either positive or negative. Negative sparsity implies a weak Allee effect, and the population survives in some domain and diverges otherwise. Positive sparsity gives a strong Allee effect, and the population extinct without any condition. The influence of Allee effects on the existence and persistence of positive steady states as well as global bifurcation diagrams is presented. The method of sub-super solutions is used for analyzing equations. The stability conditions and the region of positive solutions (multiple solutions may exist) are presented. When the diffusion is absent, we consider the model with and without harvesting, which are initial value problems (IVPs) and study the local stability analysis and present bifurcation analysis. We present a number of numerical examples to verify analytical results.

scholarly journals Coupled THM and Matrix Stability Modeling of Hydroshearing Stimulation in a Coupled Fracture-Matrix Hot Volcanic System

2018 ◽  
Vol 2018 ◽  
pp. 1-15 ◽  
Author(s):  
Yong Xiao ◽  
Jianchun Guo ◽  
Hehua Wang ◽  
Lize Lu ◽  
John McLennan ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Conduction ◽  
Dominant Role ◽  
Injection Well ◽  
Time Step ◽  
Volcanic System ◽  
Induced Stress ◽  
The Matrix ◽  
Matrix Stability ◽  
The Stability

A coupled thermal-hydraulic-mechanical (THM) model is developed to simulate the combined effect of fracture fluid flow, heat transfer from the matrix to injected fluid, and shearing dilation behaviors in a coupled fracture-matrix hot volcanic reservoir system. Fluid flows in the fracture are calculated based on the cubic law. Heat transfer within the fracture involved is thermal conduction, thermal advection, and thermal dispersion; within the reservoir matrix, thermal conduction is the only mode of heat transfer. In view of the expansion of the fracture network, deformation and thermal-induced stress model are added to the matrix node’s in situ stress environment in each time step to analyze the stability of the matrix. A series of results from the coupled THM model, induced stress, and matrix stability indicate that thermal-induced aperture plays a dominant role near the injection well to enhance the conductivity of the fracture. Away from the injection well, the conductivity of the fracture is contributed by shear dilation. The induced stress has the maximum value at the injection point; the deformation-induced stress has large value with smaller affected range; on the contrary, thermal-induced stress has small value with larger affected range. Matrix stability simulation results indicate that the stability of the matrix nodes may be destroyed; this mechanism is helpful to create complex fracture networks.

Numerical Investigation of Nitrate Leakage and Migration in the Soil after Rainfall

2014 ◽  
Vol 1010-1012 ◽  
pp. 429-436
Author(s):  
Jin Hua Shan ◽  
Jing Ding ◽  
Jian Feng Lu
Keyword(s):  
Heat Transfer ◽  
Thermal Power ◽  
Nitrate Salt ◽  
Storage Medium ◽  
Migration Process ◽  
Solar Thermal Power ◽  
Salt Layer ◽  
Thermal Power System ◽  
And Migration ◽  
And Storage

Nitrate salt is important heat transfer and storage medium in solar thermal power system, but nitrate salt leakage and pollution in groundwater is seldom investigated. In this paper, the nitrate salt leakage and migration in the soil after rainfall are simulated and analyzed. During the nitrate leakage process, the liquid nitrate will solidify, and then a thin solidification layer of nitrate forms. According to the simulation result, the radius of the leakage opening mainly affects the radius of nitrate solidification layer, while the leakage velocity will influence the radius and thickness of salt layer. During the nitrate migration process after rainfall, the nitrate will gradually migrate to the groundwater, and the final migration domain of nitrate in the soil will be mainly determined by the radius of nitrate solidification layer.

Efficient Two-dimensional Acoustic Wave Finite-Difference Numerical Simulation in Strongly Heterogeneous Media Using the Adaptive Mesh Refinement (AMR) Technique

Geophysics ◽  
2021 ◽  
pp. 1-76
Author(s):  
Chunli Zhang ◽  
Wei Zhang
Keyword(s):  
Finite Difference ◽  
Acoustic Wave ◽  
Adaptive Mesh Refinement ◽  
Heterogeneous Media ◽  
Mesh Refinement ◽  
Adaptive Mesh ◽  
Grid Spacing ◽  
Time Step ◽  
Velocity Models ◽  
The Stability

The finite-difference method (FDM) is one of the most popular numerical methods to simulate seismic wave propagation in complex velocity models. If a uniform grid is applied in the FDM for heterogeneous models, the grid spacing is determined by the global minimum velocity to suppress dispersion and dissipation errors in the numerical scheme, resulting in spatial oversampling in higher-velocity zones. Then, the small grid spacing dictates a small time step due to the stability condition of explicit numerical schemes. The spatial oversampling and reduced time step will cause unnecessarily inefficient use of memory and computational resources in simulations for strongly heterogeneous media. To overcome this problem, we propose to use the adaptive mesh refinement (AMR) technique in the FDM to flexibly adjust the grid spacing following velocity variations. AMR is rarely utilized in acoustic wave simulations with the FDM due to the increased complexity of implementation, including its data management, grid generation and computational load balancing on high-performance computing platforms. We implement AMR for 2D acoustic wave simulation in strongly heterogeneous media based on the patch approach with the FDM. The AMR grid can be automatically generated for given velocity models. To simplify the implementation, we employ a well-developed AMR framework, AMReX, to carry out the complex grid management. Numerical tests demonstrate the stability, accuracy level and efficiency of the AMR scheme. The computation time is approximately proportional to the number of grid points, and the overhead due to the wavefield exchange and data structure is small.

Impact of osmotic pressure on the stability of Taylor vortices

2022 ◽  
Vol 933 ◽  
Author(s):  
Rouae Ben Dhia ◽  
Nils Tilton ◽  
Denis Martinand
Keyword(s):  
Osmotic Pressure ◽  
Critical Conditions ◽  
Hydrodynamic Instabilities ◽  
Taylor Vortices ◽  
Dynamic Filtration ◽  
Analytical Criterion ◽  
Permeable Cylinders ◽  
Couette Cell ◽  
Taylor Couette ◽  
The Stability

We use linear stability analysis and direct numerical simulations to investigate the coupling between centrifugal instabilities, solute transport and osmotic pressure in a Taylor–Couette configuration that models rotating dynamic filtration devices. The geometry consists of a Taylor–Couette cell with a superimposed radial throughflow of solvent across two semi-permeable cylinders. Both cylinders totally reject the solute, inducing the build-up of a concentration boundary layer. The solute retroacts on the velocity field via the osmotic pressure associated with the concentration differences across the semi-permeable cylinders. Our results show that the presence of osmotic pressure strongly alters the dynamics of the centrifugal instabilities and substantially reduces the critical conditions above which Taylor vortices are observed. It is also found that this enhancement of the hydrodynamic instabilities eventually plateaus as the osmotic pressure is further increased. We propose a mechanism to explain how osmosis and instabilities cooperate and develop an analytical criterion to bound the parameter range for which osmosis fosters the hydrodynamic instabilities.

Population dynamics of priority geostrategic Territories of Russia in 2010-2018

2021 ◽  
Vol 12 (2) ◽  
pp. 123-142
Author(s):  
Valery V. Patsiorkovsky ◽  
Yury A. Simagin ◽  
Djamila J. Murtuzalieva
Keyword(s):  
Economic Development ◽  
Population Dynamics ◽  
Russian Federation ◽  
Far East ◽  
The Arctic ◽  
Natural Growth ◽  
North Caucasus ◽  
Socio Economic Development ◽  
The Russian Federation ◽  
And Migration

The article presents an analysis of the dynamics of the population of the priority geostrategic territories of the Russian Federation. They are highlighted in the "Strategy for the Spatial Development of the Russian Federation until 2025" as territories that are of particular importance for the development of the country as a whole and are distinguished at the same time by special life conditions and the functioning of the economy due to their geographical location. Population dynamics for such territories is both a factor determining socio-economic development and an indicator of the effectiveness of this development. The components of the population dynamics - natural growth and migration flows - are of particular importance. The article describes all four groups of priority geostrategic territories of Russia - isolated from the main territory of the country (exclaves), located in the North Caucasus and the Far East, in the Arctic zone of the Russian Federation. For each group, trends in population dynamics have been identified since the 2010 census, taking into account the components of natural growth and migration. The multidirectional aspect of the main demographic processes in the priority geostrategic territories of the country is revealed - natural growth is combined with the migration outflow of the population, and the migration inflow - with natural decline. At the same time, in the exclave and North Caucasian territories, the population is growing, and in the Far Eastern and Arctic territories it is decreasing. The features of both groups of priority geostrategic territories in comparison with Russia as a whole and of individual constituent entities of the Russian Federation and municipalities within groups of territories are shown. The latter became possible due to the use of the database "Municipal Russia", that summarises demographic statistics for all urban districts and municipal areas of the country, including those located in priority geostrategic territories. As a result of the analysis of the population dynamics, directions have been identified that can lead to an improvement in the demographic situation in the priority geostrategic territories of the country, and, accordingly, will contribute to the socio-economic development of not only these territories, but the entire Russian Federation

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