scholarly journals Metapopulation Persistence and Extinction in a Fragmented Random Habitat: A Simulation Study

Mathematics ◽  
2021 ◽  
Vol 9 (18) ◽  
pp. 2202
Author(s):  
Hashem Althagafi ◽  
Sergei Petrovskii

Habitat fragmentation is recognized as the most serious threat to biodiversity worldwide and has been the focus of intensive research for a few decades. Due to the complexity of the problem, however, there are still many issues that remain poorly understood. In particular, it remains unclear how species extinction or persistence in a fragmented habitat consisting of sites with randomly varying properties can be affected by the strength of inter-site coupling (e.g., due to migration between sites). In this paper, we address this problem by means of numerical simulations using a conceptual single-species spatially-discrete system. We show how an increase in the inter-site coupling changes the population distribution, leading to the formation of persistence domains separated by extinction domains. Having analysed the simulation results, we suggest a simple heuristic criterion that allows one to distinguish between different spatial domains where the species either persists or goes extinct.

Insects ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 135
Author(s):  
Keng-Lou James Hung ◽  
Sara S. Sandoval ◽  
John S. Ascher ◽  
David A. Holway

Global climate change is causing more frequent and severe droughts, which could have serious repercussions for the maintenance of biodiversity. Here, we compare native bee assemblages collected via bowl traps before and after a severe drought event in 2014 in San Diego, California, and examine the relative magnitude of impacts from drought in fragmented habitat patches versus unfragmented natural reserves. Bee richness and diversity were higher in assemblages surveyed before the drought compared to those surveyed after the drought. However, bees belonging to the Lasioglossum subgenus Dialictus increased in abundance after the drought, driving increased representation by small-bodied, primitively eusocial, and generalist bees in post-drought assemblages. Conversely, among non-Dialictus bees, post-drought years were associated with decreased abundance and reduced representation by eusocial species. Drought effects were consistently greater in reserves, which supported more bee species, than in fragments, suggesting that fragmentation either had redundant impacts with drought, or ameliorated effects of drought by enhancing bees’ access to floral resources in irrigated urban environments. Shifts in assemblage composition associated with drought were three times greater compared to those associated with habitat fragmentation, highlighting the importance of understanding the impacts of large-scale climatic events relative to those associated with land use change.


2014 ◽  
Author(s):  
◽  
Dan Zheng

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] Capture-recapture models have been widely used to estimate the size of a target wildlife population. There are three major sources of variations that can affect capture probabilities: time (i.e., capture probabilities vary with time or trapping occasion), behavioral response (i.e., capture probabilities vary due to a trap response of animals to the first capture), and heterogeneity (i.e., capture probabilities vary by individual animal). There are eight models regarding possible combinations of these factors, including M0, Mt, Mb, Mh, Mtb, Mth, Mbh, and Mtbh. A capture-recapture model (Mb model) was created to present the behavioral response effect. The objective Bayesian analysis for the population size was developed and compared with common maximum likelihood estimates (MLEs). Simulation results demonstrate the advantages of the objective Bayesian over MLEs. Two real examples about a deer mouse are presented and one R package (OBMbpkg) was built for application. Companion diagnostics (CDx) for personalized medicine is commonly applied to in vitro diagnostic (IVD) industry and clinical trials for specific disease or treatment with biomarkers (e.g. molecular targets). The Bayesian method with Gibbs sampler was used to estimate the potential bias caused by imperfect CDx under the targeted design, where only patients with a positive diagnosis were enrolled the clinical trials. A simulation study was conducted to evaluate the performance of the Bayesian method and to compare with the EM algorithm. The Bayesian model selection method with G-prior was used to test treatment effects of targeted drugs for patients with biomarkers under the targeted design. A simulation study was conducted to evaluate the performance of the Bayesian method and to compare it with the original method and EM method when sample size is small. Eventually a biomarker-stratified design was studied, while patients enrolled in clinical trials could be divided into two groups (i.e., those with a positive or negative diagnosis). Both the EM algorithm and Bayesian method were used to estimate the potential bias caused by imperfect CDx. Simulation results demonstrate the advantages of the Bayesian method over the original method and EM method.


Electronics ◽  
2019 ◽  
Vol 8 (8) ◽  
pp. 905 ◽  
Author(s):  
Akpolat ◽  
Dursun ◽  
Kuzucuoğlu ◽  
Yang ◽  
Blaabjerg ◽  
...  

Turkey is among the countries largely dependent on energy import. This dependency has increased interest in new and alternative energy sources. Installation of rooftop solar photovoltaic systems (RSPSs) in Turkey is increasing continuously regarding geographical and meteorological conditions. This paper presents an insight into the potential situation for Turkey and a simulation study for the RSPS designing and calculation for the faculty building at Marmara University in Istanbul. This simulation study demonstrates that 84.75-kWp grid-connected RSPS can produce remarkable power. The system is performed in detail with the PV*SOL software (Premium 2017 R8 - Test Version, Valentin Software GmbH, Berlin, Germany). Detailed financial and performance analysis of the grid-connected RSPS for faculty building with various parameters is also carried out in this study. According to the simulation results, the system supplies 13.2% of the faculty buildings’ annual electrical energy consumption. The annual savings value of faculty buildings’ electrical consumption is approximately 90,298 kWh energy which costs roughly $7296. A photovoltaic (PV) system installation for the faculty building, which has considerable potential for solar energy and sunshine duration, is indispensable for clean energy requirements and was supported by the simulation results. This paper can be considered to be a basic feasibility study prior to moving on to the implementation project.


2016 ◽  
Vol 30 (09) ◽  
pp. 1650135
Author(s):  
Sang-Hee Lee ◽  
Ohsung Kwon

Flocking behavior of animals is highly advantageous for taking food resources. The degree of the advantage is related to the ability of flock members to detect their prey and the mobility of prey individuals. In this study, to explore the relation, we constructed a model to simulate a predator flock and its randomly moving prey. The predator members have the prey detection ability, which was characterized as sensing distance, [Formula: see text], and a sensing angle, [Formula: see text]. The mobility of the prey individuals was characterized as the maximum traveling distance of an iteration time step, [Formula: see text]. The relative flock foraging efficiency, [Formula: see text], was defined as [Formula: see text]. [Formula: see text] and [Formula: see text] represent the spent time for the flock to eat all prey individuals and to uptake the last remaining 10% prey, respectively. Simulation results showed that [Formula: see text] increased, maximized, and decreased with the increase of [Formula: see text], regardless of [Formula: see text]. As the number of prey, [Formula: see text], increased, the tendency of the increasing and decreasing was diluted. The result was briefly discussed in relation to the flock foraging behavior and the development of the model toward applications for real ecosystems.


2012 ◽  
Vol 170-173 ◽  
pp. 1920-1925
Author(s):  
Chang Ge Fan ◽  
Fa Lin Zeng ◽  
De Hua Li ◽  
Lei Liu

The working principle of concrete pumping hydraulic system was analyzed. And base on the AMESim software, the complete simulation model of concrete pumping hydraulic system was built. A simulation was made to get the dynamic characteristics curve of hydraulic cylinder velocity and displacement at some specific conditions. The simulation results indicate that the model is reasonable. Comparative simulations of the pumping hydraulic system with different positions of buffer structure were carried out to study the relationship between buffer effect and the buffer position which can be used to provide theory basis for deeper study of the hydraulic shock.


1998 ◽  
Vol 120 (2) ◽  
pp. 194-200 ◽  
Author(s):  
I. Chaudhry ◽  
F. Barez

A study has been conducted to resolve wire neck break problem in a cavity-down plastic pin grid array (PPGA) packages with a specific range of parameters when subjected to temperature cycle (−55°C/+125°C). In most cases, a weak or broken neck of the wire was observed after 300 cycles of temperature cycling. The objective of this study is to determine an optimum wire loop height so that the package can pass a 1000 temperature cycles. Results of a simulation study, performed by other researchers, using a finite element model (FEM) were utilized. Their work considered the effect of temperature cycling on PPGA packages identical to those in this report. Several possible factors that can contribute to this failure mechanism were analyzed, and stresses in the wires were evaluated. The simulation results were verified by running an experiment on actual parts. The parts were subjected to temperature cycling, and data was gathered at different test points. The experimental results obtained did concur with simulation results which suggested that the area just above the ball experienced a significant level of thermal stresses, and such stresses could be reduced by determining an optimum loop height.


2013 ◽  
Vol 345 ◽  
pp. 99-103 ◽  
Author(s):  
Yong Qing Chen ◽  
Xin He Xu ◽  
Hua Ling Zhu ◽  
Shi De Ye ◽  
Liang Tao Li

Based on the MATLAB/SimHydraulics toolbox, an automatic leveling system controlled by electro-hydraulic proportional valve was simulated and researched. With the help of Hydraulic components models in the SimHydraulics toolbox, the SimHydraulics Physical Network simulation and the Simulink control system simulation was integrated used, and the Simulink modules powerful numerical processing capability helped to improve the efficiency and accuracy of the system design. The simulation results showed that:The use of SimHydraulics toolbox on the simulation study of automatic leveling system controlled by electro-hydraulic proportional valve is feasible; The adjustment time of the automatic leveling system is short and the steady-state accuracy is high based on the PID controller.


2021 ◽  
Vol 19 (1) ◽  
pp. 2-21
Author(s):  
Talha Omer ◽  
Zawar Hussain ◽  
Muhammad Qasim ◽  
Said Farooq Shah ◽  
Akbar Ali Khan

Shrinkage estimators are introduced for the scale parameter of the Rayleigh distribution by using two different shrinkage techniques. The mean squared error properties of the proposed estimator have been derived. The comparison of proposed classes of the estimators is made with the respective conventional unbiased estimators by means of mean squared error in the simulation study. Simulation results show that the proposed shrinkage estimators yield smaller mean squared error than the existence of unbiased estimators.


1997 ◽  
Vol 36 (04/05) ◽  
pp. 261-263 ◽  
Author(s):  
Jing Bai ◽  
Hongli Lu ◽  
Jupeng Zhang ◽  
Xiaoqiang Zhou

Abstract.Many studies have been done on the respiratory and the cardiovascular system. Among them, only a few are on the interaction of these two physiologic systems. To explore the mechanism of the integration of these two physiological systems, computer simulation has been done; we report the preliminary results obtained in our laboratory. In this study, a mathematical model of the cardiovascular system integrated with the respiratory mechanical system has been established. The model is based on our previous work on cardiovascular modeling. The previous lumped lungi model has been replaced by a multielement model with more detail. Inter- thoracic and abdominal pressures are modeled as external pressure sources on the related cardiovascular elements. Using this model, a sequence of simulation studies have been carried out. Different respiratory modes have been simulated and the different effects are observed in the simulation results. The results indicate that by following a certain respiratory pattern, the circulation status can be improved. These results agree with clinical observations.Keywords: Mathematical Model, Respiration Mode, Cardiovascular System, Computer Simulation, Interaction


2019 ◽  
Vol 111 ◽  
pp. 01011
Author(s):  
Toni Calabrese ◽  
Fabian Ochs ◽  
Dietmar Siegele ◽  
Georgios Dermentzis

A new compact and cost effective heating and ventilation concept for decentral renovation of small flats in multifamily houses was developed and investigated in the framework of the Austrian project “SaLüH!” through a dynamic building and HVAC simulation study based on results of laboratory measurements of functional models. The system consists of a façade integrated supply air/exhaust air heat pump equipped with a desuperheater allowing to increase the heating power and to add more freedom to control the system. The simulation results show that such a system is able to improve the thermal comfort of the flat (compared to the standard heating concept without desuperheater) with good indoor air quality and satisfying energy performance. The proposed system - because of its versatility and compactness - represents an ideal solution for decentral renovation of flats in multi-family houses, especially in case of limited space inside the flat and if central solutions are not possible for technical, economic or social reasons.


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