population system
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Symmetry ◽  
2021 ◽  
Vol 13 (12) ◽  
pp. 2252
Author(s):  
Wenke Wang ◽  
Le Li ◽  
Xuejun Yi ◽  
Chuangxia Huang

One fundamental step towards grasping the global dynamic structure of a population system involves characterizing the convergence behavior (specifically, how to characterize the convergence behavior). This paper focuses on the neutral functional differential equations arising from population dynamics. With the help of monotonicity techniques and functional methods, we analyze the subtle relations of both the ω-limited set and special point. Meanwhile, we prove that every bounded solution converges to a constant vector, as t tends to positive infinity. Our results correlate with the findings from earlier publications, and our proof yields an improved Haddock conjecture.


2021 ◽  
Vol 31 (14) ◽  
Author(s):  
Irina Bashkirtseva ◽  
Tatyana Perevalova ◽  
Lev Ryashko

A problem of the mathematical modeling and analysis of noise-induced transformations of complex oscillatory regimes in hierarchical population systems is considered. As a key example, we use a three-dimensional food chain dynamical model of the interacting prey, predator, and top predator. We perform a comparative study of the impacts of random fluctuations on three key biological parameters of prey growth, predator mortality, and the top predator growth. A detailed investigation of the stochastic excitement, noise-induced transition from order to chaos, and various scenarios of extinction is carried out. Constructive abilities of the semi-analytical method of confidence domains in the analysis of the noise-induced extinction are demonstrated.


2021 ◽  
Vol 13 (19) ◽  
pp. 10902
Author(s):  
Ionel Muntele ◽  
Marinela Istrate ◽  
Raluca Ioana Horea-Șerban ◽  
Alexandru Banica

The deep demographic crisis that Romania has been going through, like most Eastern European states, requires complex analyses. The present study aims at analyzing the numerical evolution of the rural population of Romania, extended for more than 100 years (1912–2020), on the basis of which a multivariate analysis was subsequently performed. The manifestation of specific patterns of territorial evolution and the identification of the incidence of some physical–geographical and socio-economic factors are investigated by means of the dynamics of certain distinct processes, such as rural depopulation or ability to adapt to various transitions. The identification of the fragile and dynamic areas allows discussions on the need for public policies better oriented towards mending excesses, illustrated by the persistence of some gaps, in terms of access to basic services. At the same time, the identification of trends towards a shrinking population system, with an increasingly evident concentration of the population in peri-urban areas or along major transport routes, calls for specific policies geared more towards environmental management in depopulated and depopulating areas, or towards creating the conditions for sustainable spatial planning in high-density areas. For the time being, the disadvantaged areas are rather ignored, while the extension of metropolitan areas is rather chaotic and poorly regulated.


2021 ◽  
Vol 47 ◽  
pp. 100939
Author(s):  
Koushik Garain ◽  
Partha Sarathi Mandal

Insects ◽  
2021 ◽  
Vol 12 (8) ◽  
pp. 725
Author(s):  
Petros T. Damos ◽  
Jesse Dorrestijn ◽  
Thomas Thomidis ◽  
José Tuells ◽  
Pablo Caballero

Understanding and predicting mosquito population dynamics is crucial for gaining insight into the abundance of arthropod disease vectors and for the design of effective vector control strategies. In this work, a climate-conditioned Markov chain (CMC) model was developed and applied for the first time to predict the dynamics of vectors of important medical diseases. Temporal changes in mosquito population profiles were generated to simulate the probabilities of a high population impact. The simulated transition probabilities of the mosquito populations achieved from the trained model are very near to the observed data transitions that have been used to parameterize and validate the model. Thus, the CMC model satisfactorily describes the temporal evolution of the mosquito population process. In general, our numerical results, when temperature is considered as the driver of change, indicate that it is more likely for the population system to move into a state of high population level when the former is a state of a lower population level than the opposite. Field data on frequencies of successive mosquito population levels, which were not used for the data inferred MC modeling, were assembled to obtain an empirical intensity transition matrix and the frequencies observed. Our findings match to a certain degree the empirical results in which the probabilities follow analogous patterns while no significant differences were observed between the transition matrices of the CMC model and the validation data (ChiSq = 14.58013, df = 24, p = 0.9324451). The proposed modeling approach is a valuable eco-epidemiological study. Moreover, compared to traditional Markov chains, the benefit of the current CMC model is that it takes into account the stochastic conditional properties of ecological-related climate variables. The current modeling approach could save costs and time in establishing vector eradication programs and mosquito surveillance programs.


2021 ◽  
Vol 53 (2) ◽  
pp. 166-181
Author(s):  
Niswah Yanfa Nabilah Syams ◽  
Hadi Sumarno ◽  
Paian Sianturi

Various mathematical models have been developed to describe the transmission of malaria disease. The purpose of this study was to modify an existing mathematical model of malaria disease by using a CTMC stochastic model. The investigation focused on the transition probability, the basic reproduction number (R0), the outbreak probability, the expected time required to reach a disease-free equilibrium, and the quasi-stationary probability distribution. The population system will experience disease outbreak if R0>1, whereas an outbreak will not occur in the population system if R0≤1. The probability that a mosquito bites an infectious human is denoted as k, while θ is associated with human immunity. Based on the numerical analysis conducted, k and θ have high a contribution to the distribution of malaria disease. This conclusion is based on their impact on the outbreak probability and the expected time required to reach a disease-free equilibrium.


2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Xiaojun Guo ◽  
Rui Zhang ◽  
Naiming Xie ◽  
Jingliang Jin

Scientific prediction and accurate grasp of the future trend of population change are conducive to the formulation of different population policies at different stages, so as to alleviate the adverse effects of the aging population on society and provide scientific theoretical reference for controlling the population size and making policy. Considering that the population system is affected by many complex factors and the structural relationship among these factors is complex, it can be regarded as a typical dynamic grey system. In this paper, the fractional-order GM (1, 1) model and the fractional-order Verhulst model are established, respectively, based on the statistical data of China's population indices from 2015 to 2019 to forecast the population size and the change trend of population structure of China from 2015 to 2050 in the short-term and medium- to long-term. The forecast results show that China’s population will grow in an inverse S shape from 2015 to 2050, when the total population will reach 1.43 billion. Moreover, during this period, the birth rate and natural growth rate of population will decrease year by year, and the proportion of aging population and the dependency ratio of population will increase year by year. Besides, the problem of aging population is going to become increasingly serious. The application of grey system method to population prediction can mine the complex information contained in the population number series. Meanwhile, the fractional-order accumulation can weaken the randomness of the original data series and reduce the influence of external disturbance factors, so it is a simple and effective population prediction method.


Insects ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 503
Author(s):  
Petros Damos ◽  
José Tuells ◽  
Pablo Caballero

A central issue of public health strategies is the availability of decision tools to be used in the preventive management of the transmission cycle of vector-borne diseases. In this work, we present, for the first time, a soft system computing modeling approach using two dynamic artificial neural network (ANNs) models to describe and predict the non-linear incidence and time evolution of a medically important mosquito species, Culex sp., in Northern Greece. The first model is an exogenous non-linear autoregressive recurrent neural network (NARX), which is designed to take as inputs the temperature as an exogenous variable and mosquito abundance as endogenous variable. The second model is a focused time-delay neural network (FTD), which takes into account only the temperature variable as input to provide forecasts of the mosquito abundance as the target variable. Both models behaved well considering the non-linear nature of the adult mosquito abundance data. Although, the NARX model predicted slightly better (R = 0.623) compared to the FTD model (R = 0.534), the advantage of the FTD over the NARX neural network model is that it can be applied in the case where past values of the population system, here mosquito abundance, are not available for their forecasting.


2021 ◽  
Vol 10 (1) ◽  
pp. 52-56
Author(s):  
Tri Bayu Purnama ◽  
Samsul Askhori ◽  
Devi Juliana Pohan ◽  
Dwichy Augie

Dental health remains a public health problem with increased the prevalence of dental problems from 2007 to 2013. The problem is highest in the early adolescent age group. A dental problem occurs due to lack of behavior on the routine toothbrush (2.8%). The purpose of this study was to describe dental problems in Islamic boarding schools in Medan. This study used a cross sectional design in seven Islamic boarding schools in Medan with a total sample of 436 students in the 5.319 total population. System random sampling was applied in this study and the questionnaire was distributed to sample. The data analysis used was descriptive frequency. The results showed that the behavior of brushing teeth based on age group was highest in the early adolescent group in the category of brushing teeth in the morning (78%) and afternoon (92%). Based on gender, both men and women showed the highest tooth brushing behavior in the morning (37.8%; 40.4%) and afternoon (45.9%; 46.6%). Dental health problems by age group were included in the category of healthy teeth (49.1%). Based on gender also showed dental problems for both men and women (25.9%; 24.1%) in the category of healthy teeth. Dental health among female students is still found to have dental health problems caused by the behavior of brushing teeth that is not in accordance with the recommendations of the Ministry of Health, namely after breakfast and before going to bed at night.


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