Global qualitative analysis of a predator–prey system with Allee effect on the prey species

In this paper, the Allee effect is incorporated into a predator–prey model with linear functional response. Compared with the predator–prey model without the Allee effect, it is found that the Allee effect of the prey species increases the extinction risk of both the prey and predator. If the Allee effect of the prey species is strong and the mortality of the predator species is relatively low, then the prey and predator cannot coexist after the predator invasion. Moreover, it is shown that the model with Allee effect undergoes the heteroclinic loop bifurcation and subcritical and supercritical Hopf bifurcations. With the brokenness of the heteroclinic loop, a stable or unstable limit cycle will appear. The Allee effect of the prey species can lead to unstable or stable periodic fluctuations. It is also found that the positive equilibrium of the model could change from stable to unstable, and then disappear when the strength of Allee effect increases continuously from zero.     

Periodic solutions for a delayed predator–prey system with stage-structured predator on time scales

In this paper, a modified delayed predator–prey system with stage structure for predator is proposed and studied, which generalizes and incorporates as special cases some known models. With the help of continuation theorem based on the Gaines and Mawhin coincidence degree theory, we investigate the existence of periodic solutions for the proposed delayed predator–prey system with stage-structured predator and two kinds of functional responses (called Holling III functional response and Beddington–DeAngelis functional response) on time scales. In particular, when the time scale is chosen as the set of the real numbers or the integers, the existence of the periodic solutions of the corresponding continuous-time and discrete-time models follows.     

Epidemics spreading in predator–prey systems

In this paper, we consider an ecosystem in which two disease-affected populations thrive and in which the epidemics can spread from one species to the other one by contact. The feasibility and stability conditions of the equilibria of the system are investigated analytically. The model does not possess Hopf bifurcations. Numerical simulations are performed to investigate the role of the main epidemiological and demographic parameters in the model, thus discovering that the predation of healthy or diseased predators on an infected prey allows some kind of control of the prey, if the latter, for instance, represents a pest.     

Global solution of a diffusive predator–prey model with prey-taxis

We consider the prey-taxis system:

$\left\{\begin{array}{cc}{u}_t=d_1\Delta u?\chi ??(u?v)+u(a?\mu u)+buf\left(v\right),\hfill & x\in \Omega ,t>0,\hfill \\ v_t=d_2\Delta v+v(c?\beta v)?uf\left(v\right),\hfill & x\in \Omega ,t>0\hfill \end{array}\right.$

in a smoothly bounded domain $\Omega ?{\mathbb{R}}^n$, with zero-flux boundary condition, where $a,d_1,d_2,\chi ,\mu ,b,c$ are positive constants and $\beta$ is a non-negative constant. We first investigate the global existence and local boundedness of solution for the case $\beta =0$. Moreover, when $\beta >0$, we show that the solution exists globally and is uniformly bounded provided $\mu$ is large enough.     

Stability analysis of a predator–prey model in wireless sensor network

Limited availability of energy within the network motes in wireless sensor network became a critical issue; therefore, making a perfect use of energy is necessary. A widely employed energy-saving technique is to place motes in sleep mode, corresponding to low-power consumption as well as to reduce operational capabilities. In this paper, we propose a mathematical model based on predator–prey dynamics to analyse the impact of energy conservation in the context of worm attacks in such network. We analyse the system to obtain different equilibrium points and then found the conditions for their stability. Lastly, some numerical simulations are given to illustrate the analytical results.     

Towards inverse modeling of turbidity currents: The inverse lock-exchange problem

A new approach is introduced for turbidite modeling, leveraging the potential of computational fluid dynamics methods to simulate the flow processes that led to turbidite formation. The practical use of numerical flow simulation for the purpose of turbidite modeling so far is hindered by the need to specify parameters and initial flow conditions that are a priori unknown. The present study proposes a method to determine optimal simulation parameters via an automated optimization process. An iterative procedure matches deposit predictions from successive flow simulations against available localized reference data, as in practice may be obtained from well logs, and aims at convergence towards the best-fit scenario. The final result is a prediction of the entire deposit thickness and local grain size distribution. The optimization strategy is based on a derivative-free, surrogate-based technique. Direct numerical simulations are performed to compute the flow dynamics. A proof of concept is successfully conducted for the simple test case of a two-dimensional lock-exchange turbidity current. The optimization approach is demonstrated to accurately retrieve the initial conditions used in a reference calculation.     

基于捕食-被捕食粒子群优化的模糊聚类

粒子群优化聚类算法具有参数简单,收敛快等优势,但也有局部极值问题。为解决此问题,提出一种基于捕食-被捕食的粒子群优化模糊聚类算法且聚类中心采用密度函数初始化。捕食者追逐被捕食者中心,加速收敛,而被捕食者逃离捕食者,促进多样性,以防局部极值出现。实验测试数据表明,算法具有防止局部极值、收敛快、全局寻优能力强等性能优势,能够比较好客观地反映现实世界。     

Parallel predator–prey interaction for evolutionary multi-objective optimization

Over the last decade, the predator?Cprey model (PPM) has emerged as an alternative algorithmic approach to multi-objective evolutionary optimization, featuring a very simple abstraction from natural species interplay and extensive parallelization potential. While substantial research has been done on the former, we for the first time review the PPM in the light of parallelization: We analyze the architecture and classify its components with respect to a recent taxonomy for parallel multi-objective evolutionary algorithms. Further, we theoretically examine benefits of simultaneous predator collaboration on a spatial population structure and give insights into solution emergence. On the prey level, we integrate a gradient-based local search mechanism to exploit problem independent parallelization and hybridize the model in order to achieve faster convergence and solution stability. This way, we achieve a good approximation and unfold further parallelization potential for the model.     

Positive periodic solutions for the neutral ratio-dependent predator–prey model

By using a continuation theorem based on coincidence degree theory, we obtain some new sufficient conditions for the existence of positive periodic solutions for the neutral ratio-dependent predator–prey model with Holling type II functional response.     

Towards a bipartite graph modeling of the internet topology

Modeling the properties of the Internet topology aims at generating large scale artificial IP networks that mimic properties of real ones for simulation purposes. Current models typically consider the Internet as a simple graph where edges are point-to-point connections between routers. This approach does not take into account point-to-multipoint connections that exist at lower layers in the network, e.g. layer-2 clouds, such as Ethernet switches or MPLS networks. Instead, such physical point-to-multipoint connections are modeled as several logical IP level point-to-point connections.     

Improvements to single-objective constrained predator–prey evolutionary optimization algorithm

In predator–prey algorithm, a relatively small number of predators (“lions”) and a much larger number of prey (“antelopes”) are randomly placed on a two dimensional lattice with connected ends representing an unfolded surface of a torus. The predators are partially or completely biased towards one or more objectives, based on which each predator kills the weakest prey in its neighborhood. A stronger prey created through evolution replaces this prey. In case of constrained problems, the sum of constraint violations serves as an additional objective. Modifications of the basic predator–prey algorithm have been implemented in this paper regarding the selection procedure, apparent movement of the predators, and mutation strategy. Further modifications have been made making the algorithm capable of handling multiple equality and inequality constraints. The final modified algorithm was tested on standard linear/nonlinear and constrained/unconstrained single-objective optimization problems.     

Entity-life modeling: modeling a thread architecture on the problem environment

With Java threads and the wider availability of multiprocessors, more programmers are confronted with multithreading. Concurrent threads let you take advantage of multiprocessors to speed up execution. They are also useful on a single processor, where one thread can compute while others wait for external input. Entity-life modeling is an approach for designing multithread programs.     

Existence and stability of periodic solution of a predator–prey model with state-dependent impulsive effects

According to integrated pest management for pests, we investigate the dynamic behavior of a class predator–prey system with state-dependent impulsive effects by releasing natural enemies and spraying pesticide at different thresholds. Using the Poincaré map and the properties of the Lambert W function, we prove the sufficient conditions for the existence and stability of semi-trivial solutions and positive periodic solutions. Numerical results are carried out to illustrate the feasibility of our main results.     

An application of dynamic modeling to the sea shore rotation planning problem in the navy

The navy sea shore rotation planning problem is presented as multicriteria dynamic network optimization problem with side constraints. Using the simplex primal optimization code of Professor J. Kennington and a specially designed heuristic rounding routine we developed a computer model to run practical problems with different input parameters.     

Continuous and impulsive harvesting strategies in a stage-structured predator–prey model with time delay

In this paper, the continuous and impulsive harvesting policies are considered in a predator–prey system with stage-structure. In the case in which a continuous harvesting is used, it is shown that the mature predator becomes extinct under appropriate conditions. In the case in which an impulsive harvesting is used, using the discrete dynamical system determined by the stroboscopic map, we obtain the mature predator-eradication periodic solution of the system which is globally attractive. The conditions of permanence are established by the method of comparison involving multiple Liapunov functions and auxiliary function. These results indicate that: a short period of pulse harvest is a sufficient condition for the eradication of the population; the impulsive harvest policy is more effective than the continuous one from eradicating predator point of view. Our results offer a more economical and safe strategy in controlling pest in contrast with biological control and chemical control. Furthermore, we give a summary of the dynamic behavior when the impulsive period takes values in different intervals. Finally, numerical results show that the impulsive system we considered has more complex dynamics including quasi-periodic oscillation and chaos.     

Towards mining the organizational structure of a dynamic event scenario

The increasing volume and value of data is an important enabler for data science. In this study, we consider the event data, i.e. information on things that happen in organizations, machines, systems and people’s lives. Each event refers to a well-defined activity in a certain business process execution, the resource (i.e. person or device) executing or initiating the activity, the timestamp of the event, as well as to various data elements recorded with the event (e.g. the geo-location of an activity). Process mining aims to analyze event data, in order to mine knowledge that can contribute to improving a business process behavior. In particular, the focus of this study is on organizational mining, that is a sub-field of process mining that aims at understanding the life cycle of a dynamic organizational structure (i.e. a configuration of organization units) and the interactions among co-workers (resources) arising from the analysis of real-world event logs. The innovative contribution of this study is that the organizational mining goal is here achieved by combining concepts from process mining, stream mining and social network analysis. This combination is an original contribution of this study, not still explored in organizational mining field. In an assessment, benchmark event data are explored, in order to understand how the presented solution allows us to identify the life cycle a dynamic organizational structure.     

Towards privacy-driven design of a dynamic carpooling system

Dynamic carpooling (also known as instant or ad-hoc ridesharing) is a service that arranges one-time shared rides on very short notice. This type of carpooling generally makes use of three recent technological advances: (i) navigation devices to determine a driver’s route and arrange the shared ride; (ii) smartphones for a traveller to request a ride from wherever she happens to be; and (iii) social networks to establish trust between drivers and passengers. However, the mobiquitous environment in which dynamic carpooling is expected to operate raises several privacy issues. Among all the personal identifiable information, learning the location of an individual is one of the greatest threats against her privacy. For instance, the spatio-temporal data of an individual can be used to infer the location of her home and workplace, to trace her movements and habits, to learn information about her centre of interests or even to detect a change from her usual behaviour. Therefore, preserving location privacy is a major issue to be able to leverage the possibilities offered by dynamic carpooling. In this paper we use the principles of privacy-by-design to integrate the privacy aspect in the design of dynamic carpooling, henceforth increasing its public (and political) acceptability and trust.     

Towards modeling popularity of microblogs

As one kind of social media, microblogs are widely used for sensing the real-world. The popularity of microblogs is an important measurement for evaluation of the influencial of pieces of information. The models and modeling techniques for popularity of microblogs are studied in this paper. A huge data set based on Sina Weibo, one of the most popular microblogging services, is used in the study. First, two different types of popularity, namely number of retweets and number of possible views are defined, while their relationships are discussed. Then, the temporal dynamics, including lifecycles and tipping-points, of tweets’ popularity are studied. For modeling the temporal dynamics, a piecewise sigmoid model is used. Empirical studies show the effectiveness of our modeling methods.