BUET : Departmental Website

Dr. Ishrat Zahan

Associate Professor
Specialization

Population Ecology, Computational Fluid Dynamics, Heat Transfer, Fuzzy Mathematics

Academic Biography

Dr. Ishrat Zahan is an Assistant Professor in the Department of Mathematics at Bangladesh University of Engineering and Technology. She has been a regular faculty of this University since 2012. She received her PhD degree in Mathematics in the field of Population Ecology in 2022 and M. Phil degree in Mathematics in the field of Computational Fluid Dynamics in 2017 from the Bangladesh University of Engineering and Technology. She also achieved her Master of Science and Bachelor of Science degrees in Mathematics from the University of Dhaka, Bangladesh, in 2008 and 2010, respectively. The research interests of Dr. Ishrat Zahan are in Modeling in Mathematical Ecology, Computational Fluid Dynamics, Analysis of Partial Differential Equations, and Fuzzy Mathematics. Specifically, Dr. Ishrat Zahan focuses on establishing theoretical results of rigorous mathematical models and verifying the results by simulating the problems. Fortran, MATLAB, and COMSOL Multiphysics are the computing surfaces to write the programming codes, analyze data, and to develop the algorithm.

Contact

Email: ishratzahan@math.buet.ac.bd

Educational Information

Ph.D., Bangladesh University of Engineering and Technology (BUET) , 2022
M.Phil, Bangladesh University of Engineering and Technology (BUET), 2017
MS in Applied Mathematics, University of Dhaka (DU), 2009
B. Sc (Hon's) in Mathematics, University of Dhaka (DU), 2007
H.S.C., Jamalpur Govt Ashek Mahmud College, 2002
S.S.C., Jamalput Govt Girls' High School, 2000

Research Accounts

Researchgate: https://www.researchgate.net/profile/Ishrat-Zahan-3
Google scholar: https://scholar.google.com/citations?hl=en
Scopus: https://www.scopus.com/authid/detail.uri?authorId=57202728700
ORCID: https://orcid.org/0000-0002-1503-2633

Honors And Awards

Bangabandhu Science and Technology Fellowship 2020-2021 for Ph. D. Program Ministry of Science and Technology 2020
Academic Scholarship University of Dhaka 2009

Professional Memberships

Faculty of Science BUET
Bangladesh Mathematical Society 742
Bangladesh Society for Mathematical Biology LM0018
Association of BUET Alumni 20222311012L
Association of Bangladeshi Women in Mathematics L 0030

Research Interests

Population Ecology
Theoretical and Computational Biology
Computational Fluid Dynamics

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Ishrat Zahan, Md. Kamrujjaman *Evolution of dispersal and the analysis of a resource flourished population model with harvesting* Science Direct, 8 May, 2024 Publication Type: Journal View Summary/Abstract , Publication Link This study explores a spatially distributed harvesting model that signifies the outcome of the competition of two species in a heterogeneous environment. The model is controlled by reaction-diffusion equations with resource-based diffusion strategies. Two different situations are maintained by the harvesting effects: when the harvesting rates are independent in space and do not exceed the intrinsic growth rate; and when they are proportional to the time-independent intrinsic growth rate. In particular, the competition between both species differs only by their corresponding migration strategy and harvesting intensity. We have computed the main results for the global existence of solutions that represent either coexistence or competitive exclusion of two competing species depending on the harvesting levels and different imposed diffusion strategies. We also established some estimates on harvesting efforts for which coexistence is apparent. Also, some numerical results are exhibited in one and two spatial dimensions, which shed some light on the ecological implementation of the model.
I. Zahan, R. Nasrin, S. Hasan *Numerical Simulation of Heat Transfer Performance of Ionanofluid Flow inside Two Connected Oblique Triangular Enclosure* SSRN, May, 2023 Publication Type: Conference View Summary/Abstract , Publication Link Utilizing ionanofluid is one of the best ways to improve the thermal performance of working fluids for storage, energy conversion, and transportation in contemporary thermal systems. It is a group of nano dispersions where ionic liquids create the continuous phase. This article's goal is to examine how various nanofluids perform when the natural convection of long single-walled carbon nanotubes (SWCNTs) nanoparticle occurring in a cavity which is made up of two connected oblique triangles. The cavity has a thin cold wall (Tc) with angular diameter √2m. Both halves of the left and bottom walls are heated and kept at constant temperature (Th). The remaining walls are insulated. The Navier-Stokes equations and energy conservation equation with appropriate boundary conditions are applied for modeling the considered physics and FEM is used to solve it. The heat-transferring mediums are assumed as the ionanofluid of SWCNT and 1-butyl-3-methylimidazolium bis{(trifluoromethyl)sulfonyl}imide ([C4mim][NTf2]) ionic liquid (IL), nanofluid of water-SWCNT and pure water. The effective parameters in a range of Rayleigh number (103 ≤ 𝑅𝑎 ≤ 106 ) and solid concentration (0.1% ≤ 𝜙 ≤ 5%) are considered. The findings show that due to higher thermal conductivity and appealing rheological features of ionanofluid, the heat transfer rate is found significantly higher than nanofluid and pure water. A higher solid concentration of SWCNTs represents greater values of mean Nusselt number. Additionally, fluid velocity and heat transfer rate increase at larger values of Ra
Ishrat Zahan, Md. Kamrujjaman, Md. Abdul Alim, Md. Shahidul Islam, Taufiquar Khan *The evolution of resource distribution, slow diffusion, and dispersal strategies in heterogeneous populations* frontiers, June , 2023 Publication Type: Journal View Summary/Abstract , Publication Link Population diffusion in river-ocean ecologies and for wild animals, including birds, mainly depends on the availability of resources and habitats. This study explores the dynamics of the resource-based competition model for two interacting species in order to investigate the spatiotemporal effects in a spatially distributed heterogeneous environment with no-flux boundary conditions. The main focus of this study is on the diffusion strategy, under conditions where the carrying capacity for two competing species is considered to be unequal. The same growth function is associated with both species, but they have different migration coefficients. The stability of global coexistence and quasi-trivial equilibria are also studied under different conditions with respect to resource function and carrying capacity. Furthermore, we investigate the case of competitive exclusion for various linear combinations of resource function and carrying capacity. Additionally, we extend the study to the instance where a higher migration rate negatively impacts population growth in competition. The efficacy of the model in the cases of one- and two-dimensional space is also demonstrated through a numerical study.
Ishrat Zahan, Md. Kamrujjaman, Md. Abdul Alim, Md. Shahidul Islam, Taufiquar Khan *The evolution of resource distribution, slow diffusion, and dispersal strategies in heterogeneous populations* frontiers, 26 June, 2023 Publication Type: Journal View Summary/Abstract , Publication Link Population diffusion in river-ocean ecologies and for wild animals, including birds, mainly depends on the availability of resources and habitats. This study explores the dynamics of the resource-based competition model for two interacting species in order to investigate the spatiotemporal effects in a spatially distributed heterogeneous environment with no-flux boundary conditions. The main focus of this study is on the diffusion strategy, under conditions where the carrying capacity for two competing species is considered to be unequal. The same growth function is associated with both species, but they have different migration coefficients. The stability of global coexistence and quasi-trivial equilibria are also studied under different conditions with respect to resource function and carrying capacity. Furthermore, we investigate the case of competitive exclusion for various linear combinations of resource function and carrying capacity. Additionally, we extend the study to the instance where a higher migration rate negatively impacts population growth in competition. The efficacy of the model in the cases of one- and two-dimensional space is also demonstrated through a numerical study.
Ishrat Zahan, Md. Kamrujjaman, Saleh Tanveer *Mathematical Study of a Resource-Based Diffusion Model with Gilpin–Ayala Growth and Harvesting* Springer Nature, 15 September, 2022 Publication Type: Journal View Summary/Abstract , Publication Link This paper focuses on a Gilpin–Ayala growth model with spatial diffusion and Neumann boundary condition to study single species population distribution. In our heterogeneous model, we assume that the diffusive spread of population is proportional to the gradient of population per unit resource, rather than the population density itself. We investigate global well-posedness of the mathematical model, determine conditions on harvesting rate for which non-trivial equilibrium states exist and examine their global stability. We also determine conditions on harvesting that leads to species extinction through global stability of the trivial solution. Additionally, for time periodic growth, resource, capacity and harvesting functions, we prove existence of time-periodic states with the same period. We also present numerical results on the nature of nonzero equilibrium states and their dependence on resource and capacity functions as well as on Gilpin–Ayala parameter θ. We conclude enhanced effects of diffusion for small θ which in particular disallows existence of nontrivial states even in some cases when intrinsic growth rate exceeds harvesting at some locations in space for which a logistic model allows for a nonzero equilibrium density.
Ishrat Zahan, Md. Kamrujjaman, Md. Abdul Alim, Muhammad Mohebujjaman, Taufiquar Khan *Dynamics of heterogeneous population due to spatially distributed parameters and an ideal free pair* frontiers, 09 August , 2022 Publication Type: Journal View Summary/Abstract , Publication Link Population movements are necessary to survive the individuals in many cases and depend on available resources, good habitat, global warming, climate change, supporting the environment, and many other issues. This study explores the spatiotemporal effect on the dynamics of the reaction-diffusion model for two interacting populations in a heterogeneous habitat. Both species are assumed to compete for different fundamental resources, and the diffusion strategies of both organisms follow the resource-based diffusion toward a positive distribution function for a large variety of growth functions. Depending on the values of spatially distributed interspecific competition coefficients, the study is conducted for two cases: weak competition and strong competition, which do not perform earlier in the existing literature. The stability of global attractors is studied for different conditions of resource function and carrying capacity. We investigated that in the case of weak competition, coexistence is attainable, while strong competition leads to competitive exclusion. This is an emphasis on how resource-based diffusion in the niche impacts selection. When natural resources are in sharing, either competition or predator-prey interaction leads to competitive exclusion or coexistence of competing species. However, we concentrate on the situation in which the ideal free pair is achieved without imposing any other additional conditions on the model’s parameters. The effectiveness of the model is accomplished by numerical computation for both one and two space dimension cases, which is very important for biological consideration
Ishrat Zahan, Md. Kamrujjaman, Md. Abdul Alim *A reaction-advection-diffusion model in spatial ecology: theoretical and computational analysis* Khulna University Studies, 26 September, 2022 Publication Type: Journal View Summary/Abstract , Publication Link In a confined heterogeneous habitat with two species interacting for common resources, the research analyzes a reaction-advection-diffusion type dispersal model with homogeneous Neumann boundary conditions for generalized growth functions. Both species follow the same symmetric growths law, but their dispersal strategies and advection rates are different. The following pattern is used to consider the competition strategy: in a bounded heterogeneous habitat, the first population disperses according to its resource functions, whereas the second population disperses according to its carrying capacity. We investigate the model in two scenarios: when carrying capacity and resource functions are non-proportional, competitive exclusion occurs, and one species drives the other to extinction in the long run for various similar and unequal carrying capacities of competing species. However, coexistence is achievable for different resource distribution consumption if the resource distribution and the carrying capacity phase of the second species are non-constant and similar. A series of numerical computations are used to demonstrate the model’s efficacy in oneand two-dimensional instances, which is particularly significant for environmental considera
I. Zahan, R. Nasrin, Shatay Khatun *Thermal performance of ternary-hybrid nanofluids through a convergent-divergent nozzle using distilled water - ethylene glycol mixtures* Elsevier, 12 July, 2022 Publication Type: Journal View Summary/Abstract , Publication Link A computational analysis is conducted based on ternary-nanoparticles performance for base fluid mixture through a convergent-divergent (CD) nozzle. Since the thermal phenomena through a CD nozzle exposes many attention-grabbing performances, it deserves additional investigation for laminar flow characteristics. Using ternary-nanoparticles at different base fluid mixture makes the study more robust and interesting to analyze the real situation better. In this study, the properties of cobalt (Co), silver (Ag), and zinc (Zn) nanoparticles along with base fluid mixtures of distilled-water (DW) and ethylene glycol (EG) as (100:0), (60:40), (50:50), and (0:100), are employed. A wide range of inlet velocity, solid concentrations, nanoparticle size and magnitude of nanoparticle shape factor is considered in this research. The mixtures of nanoparticles are considered as a ratio of (0:1/2:1/2), (1/2:0:1/2), (1/2:1/2:0), (1/6:1/6:2/3), (1/6:2/3:1/6), (2/3:1/6:1/6) and (1/3:1/3:1/3). The mathematical model is formulated using Navier-Stokes equations, energy conservation with proper boundary conditions, and solved using finite element method. Among the considered base fluid mixtures, the highest heat transfer rate is obtained for EG-Co-Ag-Zn nanofluid. A relatively higher heat transfer rate is found for all base fluid mixtures with nanoparticles ratio (1/6:2/3:1/6) compared to other combinations. Furthermore, advanced rate of thermal transport is found using laminar shape nanoparticles.
R. Nasrin, S. A. Sweety, I. Zahan *Turbulent Nanofluid Flow Analysis Passing a Shell and Tube Thermal Exchanger with Kays-Crawford Model* American Scientific Publishers, December, 2021 Publication Type: Journal View Summary/Abstract , Publication Link Temperature dissipation in a proficient mode has turned into a crucial challenge in industrial sectors because of worldwide energy crisis. In heat transfer analysis, shell and tube thermal exchangers is one of the mostly used strategies to control competent heat transfer in industrial progression applications. In this research, a numerical analysis of turbulent flow has been conceded in a shell and tube thermal exchanger using Kays-Crawford model to investigate the thermal performance of pure water and different concentrated water-MWCNT nanofluid. By means of finite element method the Reynold-Averaged Navier-Stokes (RANS) and heat transport equations along with suitable edge conditions have been worked out numerically. The implications of velocity, solid concentration, and temperature of water-MWCNT nanofluid on the fluid flow formation and heat transfer scheme have been inspected thoroughly. The numerical results indicate that the variation of nanoparticles solid volume fraction, inflow fluid velocity and inlet temperature mannerism considerably revolutionize in the flow and thermal completions. It is perceived that using 3% concentrated water-MWCNT nanofluid, higher rate of heat transfer 12.24% is achieved compared that of water and therefore to enhance the efficiency of this heat exchanger. Furthermore, a new correlation has been developed among obtained values of thermal diffusion rate, Reynolds number and volume concentration of nanoparticle and found very good correlation coefficient among the values.
I. Zahan, R. Nasrin *An Introduction to Fuzzy Topological Spaces* Scientific Research Publishing Inc, 25 May, 2021 Publication Type: Journal View Summary/Abstract , Publication Link Topology has enormous applications on fuzzy set. An attention can be brought to the mathematicians about these topological applications on fuzzy set by this article. In this research, first we have classified the fuzzy sets and topological spaces, and then we have made relation between elements of them. For expediency, with mathematical view few basic definitions about crisp set and fuzzy set have been recalled. Then we have discussed about topological spaces. Finally, in the last section, the fuzzy topological spaces which is our main object we have developed the relation between fuzzy sets and topological spaces. Moreover, this article has been concluded with the examination of some of its properties and certain relationships among the closure of these spaces.

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