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Chemical Reaction and Radiation Effects on MHD Flow of Oldroyd-B Fluid through Porous Medium Past an Exponentially Stretching Sheet with Heat Sink old - yd- b流体通过多孔介质时的化学反应和辐射效应
Pub Date : 2022-09-19 DOI: 10.1155/2022/6582295
F. Salah, Abdelmgid O. M. Sidahmed
In this article, the effect of electromagnetic force with the chemical and thermal radiation effect on the Oldroyd-B fluid past an exponentially stretched sheet with a heat sink and porous medium was studied. The governing system of nonlinear partial differential equations has transformed into a system of ordinary differential equations using similarity transformations. The system is then solved numerically using a successive linearization method. The numerical results of velocity, temperature, and concentration profiles are represented graphically. Several parameters’ effects are investigated and examined. Local Nusselt number, skin friction coefficient, porosity, Deborah numbers, and local Sherwood number numerical values are listed and analyzed. The results reveal that many parameters have a significant impact on the fluid flow profiles. The concentration profiles were considerably affected by the reaction rate parameter, and the concentration thickness of the boundary layer decreased as the reaction rate parameter increased. The results of the analysis were compared to the results of existing works and found to be in excellent agreement.
本文研究了电磁力、化学辐射效应和热辐射效应对Oldroyd-B流体通过带散热片和多孔介质的指数拉伸板的影响。利用相似变换将非线性偏微分方程控制系统转化为常微分方程控制系统。然后用连续线性化方法对系统进行数值求解。速度、温度和浓度分布的数值结果用图形表示。对几个参数的影响进行了研究和检验。列举并分析了局部努塞尔数、表面摩擦系数、孔隙率、黛博拉数和局部舍伍德数数值。结果表明,许多参数对流体流动曲线有显著影响。浓度分布受反应速率参数的影响较大,边界层浓度厚度随反应速率参数的增大而减小。分析的结果与现有工作的结果进行了比较,发现非常一致。
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引用次数: 0
Periodic Oscillations in MEMS under Squeeze Film Damping Force 挤压膜阻尼力作用下MEMS的周期振荡
Pub Date : 2022-09-02 DOI: 10.1155/2022/1498981
Juan Berón, A. Rivera
We provide sufficient conditions for the existence of periodic solutions for an idealized electrostatic actuator modeled by the Liénard-type equation x¨+FDx,ẋ+x=βV2t/1x2,x,1
本文给出了用li<s:1> + fd型方程建模的理想静电致动器周期解存在的充分条件x ,x * + x = β V 2T / 1 - x2, x∈−∞;1与β∈h +,V∈c,和fdx,X氧= κ X氧/1−× 3;κ∈λ +(称为挤膜阻尼力),或者fdx,X =
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引用次数: 2
Properties in Stage-Structured Population Models with Deterministic and Stochastic Resource Growth 具有确定性和随机资源增长的阶段结构种群模型的性质
Pub Date : 2022-08-31 DOI: 10.1155/2022/3535375
Tin Nwe Aye, Linus Carlsson
Modelling population dynamics in ecological systems reveals properties that are difficult to find by empirical means, such as the probability that a population will go extinct when it is exposed to harvesting. To study these properties, we use an aquatic ecological system containing one fish species and an underlying resource as our models. In particular, we study a class of stage-structured population systems with and without starvation. In these models, we study the resilience, the recovery potential, and the probability of extinction and show how these properties are affected by different harvesting rates, both in a deterministic and stochastic setting. In the stochastic setting, we develop methods for deriving estimates of these properties. We estimate the expected outcome of emergent population properties in our models, as well as measures of dispersion. In particular, two different approaches for estimating the probability of extinction are developed. We also construct a method to determine the recovery potential of a species that is introduced in a virgin environment.
对生态系统中的种群动态进行建模,揭示了难以通过经验手段发现的特性,例如,当一个种群暴露于采伐时,它将灭绝的概率。为了研究这些特性,我们使用包含一种鱼类和一种潜在资源的水生生态系统作为模型。特别地,我们研究了一类有饥饿和无饥饿的阶段结构种群系统。在这些模型中,我们研究了恢复力、恢复潜力和灭绝概率,并展示了在确定性和随机设置下不同采伐率如何影响这些特性。在随机设置中,我们开发了导出这些性质估计的方法。我们估计在我们的模型中出现的人口属性的预期结果,以及分散的措施。特别地,提出了两种不同的估计灭绝概率的方法。我们还构建了一种方法来确定在原始环境中引入的物种的恢复潜力。
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引用次数: 0
Quasisimple Wave Solutions of Euler's System of Equations for Ideal Gas 理想气体欧拉方程组的准简单波动解
Pub Date : 2022-08-29 DOI: 10.1155/2022/5931413
B. S. Desale, N. B. Potadar
Quasisimple wave solutions of Euler’s system of equations for ideal gas are investigated under the assumption of spherical and cylindrical symmetries. These solutions are proved to be stabilized into sound wave solutions and cavitation. It is proved that if initial conditions from outside the invariant region approach to transitional solution, then reciprocal of the self-similar parameter goes to infinity. However, when initial conditions stabilize into sound waves or cavitation, then reciprocal of self-similar parameter approaches finite value. Further, it is proved that initial conditions can be parametrized so that some of the initial conditions stabilize into sound wave solutions. The rest of the initial conditions are proved to be stabilized into cavitation. This extends the work of G. I. Taylor to the case of cavitation. It is proved that quasisimple wave solutions exist for the balance laws comprised of Euler’s system of equations in the case of cylindrically and spherically symmetric cases. The description applies to the motion of cylindrical and spherical piston in real life. In particular, self-similar description of appearance of vacuum in the motion of cylindrical and spherical piston is given.
研究了理想气体欧拉方程组在球对称和柱对称假设下的准简单波解。这些溶液被证明稳定为声波溶液和空化溶液。证明了如果初始条件从不变域外逼近过渡解,则自相似参数的倒数趋于无穷。然而,当初始条件稳定为声波或空化时,自相似参数的倒数接近有限值。进一步证明了初始条件可以参数化,使得一些初始条件稳定为声波解。其余的初始条件被证明是稳定到空化的。这将G. I. Taylor的工作扩展到空化的情况。证明了由欧拉方程组组成的平衡律在圆柱对称和球对称情况下存在准简单波动解。这种描述适用于实际生活中圆柱活塞和球面活塞的运动。特别地,给出了圆柱活塞和球面活塞运动中真空现象的自相似描述。
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引用次数: 0
Full Delay Logistic Population Model with Sustainable Harvesting 具有可持续收获的全延迟Logistic种群模型
Pub Date : 2022-08-26 DOI: 10.1155/2022/6777827
Martin Anokye, E. Donkoh, M. Ofori, Agnes Adom-Konadu
The paper studies the dynamics of a full delay-logistic population model incorporated with a proportionate harvesting function. The study discusses the stability of the model in comparison with the well-known Hutchinson logistic growth equation with harvesting function using the rate of harvesting as a bifurcation parameter to determine sustainable harvesting rate even at a bigger time delay of τ = 3.00 . In all cases, the Hutchinson equation with harvesting was forced to converge to equilibrium using an additional and a different time delay parameter, a deficiency previous researchers have failed to address when the Hutchinson model is used for this purpose. The population fluctuations are catered for with this model making the estimated maximum sustainable growth and harvest reflect realities as this model drastically reduces time-delay associated oscillations compared to the well-known Hutchinson delayed logistic models. The numerical simulations were be done using the MatLab Software.
研究了含比例收获函数的完全延迟-logistic种群模型的动力学问题。研究讨论了该模型的稳定性,并与著名的带收获函数的Hutchinson logistic增长方程进行了比较,使用收获率作为分岔参数来确定即使在较大的时滞τ = 3.00下的可持续收获率。在所有的情况下,使用一个额外的和不同的时间延迟参数,带收获的Hutchinson方程被迫收敛到平衡状态,这是以前的研究人员在使用Hutchinson模型时未能解决的一个缺陷。与著名的Hutchinson延迟逻辑模型相比,该模型极大地减少了与时滞相关的振荡,从而使估计的最大可持续增长和收获反映了现实。利用MatLab软件进行了数值模拟。
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引用次数: 1
Unsteady MHD Thin Film Flow of a Second-Grade Fluid past a Tilted Plate under the Impact of Thermal Radiation and Chemical Reaction 热辐射和化学反应作用下二阶流体通过倾斜板的非定常MHD薄膜流动
Pub Date : 2022-08-25 DOI: 10.1155/2022/9491308
M. Endalew, Masitawal Demsie Goshu, Yimer Chekol Tegegne
This paper explores the impact of chemical reaction and thermal radiation on time-dependent hydromagnetic thin-film flow of a second-grade fluid across an inclined flat plate embedded in a porous medium. The thermal radiation based on the Rosseland approximation is incorporated in the energy equation. Uniform applied magnetic field and first-order homogenous chemical reaction are included in the momentum and concentration equations, respectively. The novel mathematical flow model is constructed by using a set of partial differential equations (PDEs). The PDEs are then transformed into an equivalent set of ordinary differential equations (ODEs) and solved by applying the Laplace transform method. However, the time domain solutions are obtained by using the INVLAP subroutine of MATLAB. Physical parameters influencing thin-film velocity, temperature, and concentration are illustrated graphically, while those affecting skin friction, heat, and mass transfer rates are presented in a tabular form. It is found that thin-film velocity and temperature boost with increasing values of thermal radiation, but thin-film velocity decreases with increasing values of chemical reaction and magnetic field. The current investigation is to enhance heat and mass transfer in the design of mechanical systems involving the thin film flow of second-grade fluids over an inclined flat plate after applying thermal radiation and chemical reaction.
本文探讨了化学反应和热辐射对二级流体在多孔介质中斜平板上随时间变化的磁薄膜流动的影响。基于Rosseland近似的热辐射被纳入能量方程。动量方程和浓度方程分别包含均匀外加磁场和一阶均相化学反应。利用一组偏微分方程(PDEs)建立了新的数学流模型。然后将偏微分方程转化为一组等价的常微分方程,并应用拉普拉斯变换方法求解。然而,时域解是利用MATLAB的INVLAP子程序得到的。影响薄膜速度、温度和浓度的物理参数用图表表示,而影响表面摩擦、热和传质速率的物理参数用表格表示。发现薄膜速度和温度随热辐射的增大而增大,而随化学反应和磁场的增大而减小。目前的研究是在设计涉及二级流体薄膜在施加热辐射和化学反应后在倾斜平板上流动的机械系统时加强传热和传质。
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引用次数: 0
Fixed-Point and STILS Method to Solve a Coupled System of Transport Equations 求解耦合输运方程组的不动点和静止点法
Pub Date : 2022-08-22 DOI: 10.1155/2022/2705591
D. Sangare
In this paper, a coupled system of two transport equations is studied. The techniques are a fixed-point and Space-Time Integrated Least Square (STILS) method. The nonstationary advective transport equation is transformed to a “stationary” one by integrating space and time. Using a variational formulation and an adequate Poincare inequality, we prove the existence and the uniqueness of the solution. The transport equation with a nonlinear feedback is solved using a fixed-point method.
本文研究了两个输运方程的耦合系统。该方法是不动点法和时空积分最小二乘法。通过对空间和时间的积分,将非平稳平流输运方程转化为“平稳”输运方程。利用变分公式和充分的庞加莱不等式,证明了解的存在唯一性。采用不动点法求解非线性反馈输运方程。
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引用次数: 0
A Mathematical Model for a Transmissible Disease with a Variant 带有变异的传染性疾病的数学模型
Pub Date : 2022-08-18 DOI: 10.1155/2022/5050602
A. Otto, Morou Amidou
The outbreak of the Coronavirus (COVID-19) pandemic around the world has caused many health and socioeconomic problems, and the identification of variants like Delta and Omicron with similar and often even more transmissible modes of transmission has motivated us to do this study. In this article, we have proposed and analyzed a mathematical model in order to study the effect of health precautions and treatment for a disease transmitted by contact in a constant population. We determined the four equilibria of the system of ordinary differential equations representing the model and characterized their existence using exact methods of algebraic geometry and computer algebra. The model is studied using the stability theory for systems of differential equations and the basic reproduction number R 0 . The stability of the equilibria is analyzed using the Lienard-Chipart criterion and Lyapunov functions. The asymptotic or global stability of endemic equilibria is established, and the disease-free equilibrium is globally asymptotically stable if R 0 < 1 . Model simulation is done with Python software to study the effects of health precautions and treatment, and the results are analyzed. It is observed that if the rate of treatment and compliance with health precautions are high, the number of infections decreases in the classes of infectious and is canceled out over time. It is concluded that the high treatment rate accompanied by a suitable rate of compliance with health precautions allows for the control the disease.
全球爆发的冠状病毒(COVID-19)大流行造成了许多健康和社会经济问题,发现Delta和Omicron等具有相似且通常更具传染性的传播模式的变异,促使我们进行这项研究。在本文中,我们提出并分析了一个数学模型,以研究恒定人群中接触传播疾病的卫生预防和治疗效果。我们确定了代表该模型的常微分方程组的四个平衡点,并用代数几何和计算机代数的精确方法表征了它们的存在性。利用微分方程组的稳定性理论和基本再现数r0对模型进行了研究。利用Lienard-Chipart判据和Lyapunov函数分析了平衡点的稳定性。建立了地方病平衡点的渐近稳定性或全局稳定性,当R 0 < 1时,无病平衡点是全局渐近稳定的。利用Python软件对模型进行仿真,研究健康预防和治疗的效果,并对结果进行分析。可以观察到,如果治疗和遵守保健预防措施的比率很高,感染的数量就会减少,并随着时间的推移而被消除。结论认为,高治愈率和适当的卫生预防措施依从率可使疾病得到控制。
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引用次数: 1
Modelling and Stability Analysis of Cotton Leaf Curl Virus (CLCuV) Transmission Dynamics in Cotton Plant 棉花卷曲叶病毒(CLCuV)在棉花植株中的传播动力学建模及稳定性分析
Pub Date : 2022-08-16 DOI: 10.1155/2022/6988197
Abayneh Kebede Fantaye
In this paper, the transmission dynamics of cotton leaf curl virus (CLCuV) disease in cotton plants was proposed and investigated qualitatively using the stability theory of a nonlinear ordinary differential equations. Cotton and vector populations were both taken into account in the models. Cotton population was categorized as susceptible (A) and infected (B). The vector population was also categorized as susceptible (C) and infected (D). We established that all model solutions are positive and bounded by relevant initial conditions. The existence of unique CLCuV free and endemic equilibrium points, as well as the basic reproduction number, which is computed using the next generation matrix approach, are investigated. The conditions for the local and global asymptotic stability of these equilibrium points are then established. When the basic reproduction number is less than one, the system has locally and globally asymptotically stable CLCuV free equilibrium point, but when the basic reproduction number is more than one, the system has locally and globally asymptotically stable endemic equilibrium point. The numerical simulation findings show that lowering the infection rate of cotton vectors has a significant impact on controlling cotton leaf curl virus (CLCuV) in the time frame given.
本文利用非线性常微分方程的稳定性理论,提出了棉花卷曲叶病毒(CLCuV)在棉花植株中的传播动力学,并对其进行了定性研究。模型中都考虑了棉花种群和病媒种群。棉花种群被划分为易感(A)和感染(B),媒介种群也被划分为易感(C)和感染(D)。我们建立了所有模型解都是正的,并且受相关初始条件的限制。研究了CLCuV自由平衡点和特有平衡点的存在性,以及用下一代矩阵法计算的基本繁殖数。建立了这些平衡点的局部和全局渐近稳定的条件。当基本繁殖数小于1时,系统具有局部和全局渐近稳定的CLCuV自由平衡点;当基本繁殖数大于1时,系统具有局部和全局渐近稳定的地方性平衡点。数值模拟结果表明,在给定的时间范围内,降低棉花媒介的感染率对控制棉花卷曲叶病毒(CLCuV)有显著的影响。
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引用次数: 2
Application of Markov Chain Techniques for Selecting Efficient Financial Stocks for Investment Portfolio Construction 马尔可夫链技术在构建投资组合中选择有效金融股的应用
Pub Date : 2022-08-13 DOI: 10.1155/2022/2863302
G. Kallah-Dagadu, Victor Apatu, F. Mettle, D. Arku, Godwin Debrah
In this paper, we apply Markov chain techniques to select the best financial stocks listed on the Ghana Stock Exchange based on the mean recurrent times and steady-state distribution for investment and portfolio construction. Weekly stock prices from Ghana Stock Exchange spanning January 2017 to December 2020 was used for the study. A three-state Markov chain was used to estimate the transition matrix, long-run probabilities, and mean recurrent times for stock price movements from one state to another. Generally, the results revealed that the long-run distribution of the stock prices showed that the constant state recorded the highest probabilities as compared to the point loss and point gain states. However, the results showed that the mean recurrent time to the point gain state ranges from three weeks to thirty-five weeks approximately. Finally, Standard Chartered Bank, GCB, Ecobank, and Cal Bank emerged as the top best performing stocks with respect to the mean recurrent times and steady-state distribution, and therefore, these equities should be considered when constructing asset portfolios for higher returns.
本文运用马尔可夫链技术,基于平均循环时间和稳态分布选择加纳证券交易所上市的最佳金融股,进行投资组合构建。该研究使用了2017年1月至2020年12月期间加纳证券交易所的每周股票价格。一个三状态马尔可夫链被用来估计从一个状态到另一个状态的股票价格运动的转移矩阵、长期概率和平均循环时间。总的来说,结果表明,股票价格的长期分布表明,与点数损失和点数获得状态相比,恒定状态记录了最高的概率。然而,结果表明,平均循环时间到点增益状态约为3周至35周。最后,渣打银行、GCB、Ecobank和Cal Bank在平均循环时间和稳态分布方面表现最佳,因此,在构建更高回报的资产组合时应考虑这些股票。
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引用次数: 3
期刊
J. Appl. Math.
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