Applied Mathematics

Journal Information
ISSN / EISSN : 2152-7385 / 2152-7393
Published by: Scientific Research Publishing, Inc. (10.4236)
Total articles ≅ 2,123
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Latest articles in this journal

Ni Hua
Applied Mathematics, Volume 12, pp 32-57; https://doi.org/10.4236/am.2021.121004

Abstract:
This paper deals with a class of n-degree polynomial differential equations. By the fixed point theorem and mathematical analysis techniques, the existence of one (n is an odd number) or two (n is an even number) periodic solutions of the equation is obtained. These conclusions have certain application value for judging the existence of periodic solutions of polynomial differential equations with only one higher-order term.
Donald A. Drew
Applied Mathematics, Volume 12, pp 1-17; https://doi.org/10.4236/am.2021.121001

Abstract:
Addiction is a societal issue with many negative effects. Substances that cause addictive reactions are easily ingested and interact with some part of the neural pathway. This paper describes a mathematical model for the systemic level of a substance subject to degradation (via metabolism) and reversible binding to psychoactive sites. The model allows the determination of bound substance levels during the processing of a dose, and how the maximum level depends on system parameters. The model also allows the study of a particular periodic repetitive dosing described by a rapid ingestion if a dose is at constant intervals.
Chunyang Ma
Applied Mathematics, Volume 12, pp 18-23; https://doi.org/10.4236/am.2021.121002

Abstract:
From ancient times to the present, mathematicians have put forward many series expressions of the circular constant. Because of the importance of the circular constant to mathematical physics, the research on circular constant has never stopped. In this paper, the general function expression of the circular constant was given by studying the transient heat conduction equation. From the physical aspect of the derivation process of the circular constant expression, we can conclude that there is an infinite number of different series exist that can be used to express π.
Alhussein Mohamed
Applied Mathematics, Volume 12, pp 311-321; https://doi.org/10.4236/am.2021.124022

Abstract:
In this article, by using a fixed point theorem, we study following fourth-order three-point BVP: where f ∈ C([0,1]×[0,+∞),[0,+∞)) α ∈ [0,6) and . The main point to emphasize is that although the corresponding Green’s function is changing signs, by applying the fixed point theorem, we can still obtain at least two positive solutions and degreased solutions under certain suitable conditions.
Pascal Stiefenhofer
Applied Mathematics, Volume 12, pp 252-261; https://doi.org/10.4236/am.2021.124016

Abstract:
The purpose of this paper is to model ethical consumption behaviour based on price-dependent preferences. We motivate ethical consumption founded on the idea that ethical consumers compete for moral superiority relative to their peers by purchasing more expensive ethical conspicuous goods. An ethical consumer model in which consumers display moral consumption choices by purchasing ethical conspicuous goods is developed. This requires de_ning ethical conspicuous goods, social labels, and formalizing a set of assumptions on price-dependent ethical preferences. We show that an ethical utility function exists without relying on the usual transitivity assumption. We utilise Blashke's Rolling Theorem to show our main result.
Rômulo D. C. Santos, Sílvio M. A. Gama
Applied Mathematics, Volume 12, pp 91-129; https://doi.org/10.4236/am.2021.122008

Abstract:
In this paper, we investigate the thermal and turbulent behaviour of incompressible Newtonian flow, by numerical simulation, combining two physical phenomena, namely, the heat-transfer by mixed convection and the onset of turbulence, around different isothermal complex geometries, using the immersed boundary method coupled with the virtual physical model, in order to model the presence of the isothermal body. Boundary conditions of the Dirichlet and Neumann type are implemented. For turbulence modelling, the Smagorinsky and Spalart-Allmaras models are used, for Reynolds and Richardson numbers ranging up to 5000 and 5, respectively. This work confirms that, downstream of the immersed body, the recirculation: 1) increases with the increase in the number of Reynolds, keeping the number of Richardson constant, and 2) decreases with the increase in the number of Richardson, preserving the number of Reynolds constant. It also confirms the generation of thermal plumes moving upwards. For Reynolds numbers in the order of a few hundred and Richardson numbers around 5, it is observed, for tandem cylinders, the vortex wake being established in the downstream region. Interactions within the vortex wake, with the shear layer separated from the downstream cylinder, create two vortices near the downstream cylinder. The shear layer separating from the upstream cylinder creates a vortex behind the downstream cylinder.
W. E. Ahmed
Applied Mathematics, Volume 12, pp 75-84; https://doi.org/10.4236/am.2021.122006

Abstract:
As it is known, Binomial expansion, De Moivre’s formula, and Euler’s formula are suitable methods for computing the powers of a complex number, but to compute the powers of an octonion number in easy way, we need to derive suitable formulas from these methods. In this paper, we present a novel way to compute the powers of an octonion number using formulas derived from the binomial expansion.
Xiaolin Zeng, Tingzeng Wu
Applied Mathematics, Volume 12, pp 85-90; https://doi.org/10.4236/am.2021.122007

Abstract:
The Lanzhou index of a graph G is defined as the sum of the product between and square of du over all vertices u of G, where du and are respectively the degree of u in G and the degree of u in the complement graph of G. R(G) is obtained from G by adding a new vertex corresponding to each edge of G, then joining each new vertex to the end vertices of the corresponding edge. Lanzhou index is an important topological index. It is closely related to the forgotten index and first Zagreb index of graphs. In this note, we characterize the bound of Lanzhou index of R(T) of a tree T. And the corresponding extremal graphs are also determined.
William Menke
Applied Mathematics, Volume 12, pp 157-170; https://doi.org/10.4236/am.2021.123011

Abstract:
Generalized Least Squares (least squares with prior information) requires the correct assignment of two prior covariance matrices: one associated with the uncertainty of measurements; the other with the uncertainty of prior information. These assignments often are very subjective, especially when correlations among data or among prior information are believed to occur. However, in cases in which the general form of these matrices can be anticipated up to a set of poorly-known parameters, the data and prior information may be used to better-determine (or “tune”) the parameters in a manner that is faithful to the underlying Bayesian foundation of GLS. We identify an objective function, the minimization of which leads to the best-estimate of the parameters and provide explicit and computationally-efficient formula for calculating the derivatives needed to implement the minimization with a gradient descent method. Furthermore, the problem is organized so that the minimization need be performed only over the space of covariance parameters, and not over the combined space of model and covariance parameters. We show that the use of trade-off curves to select the relative weight given to observations and prior information is not a form of tuning, because it does not, in general maximize the posterior probability of the model parameters, and can lead to a different weighting than the procedure described here. We also provide several examples that demonstrate the viability, and discuss both the advantages and limitations of the method.
Alhussein Mohamed, Khalid Ahmed Abbakar, Abuzar Awad, Omer Khalil, Bechir Mahamat Acyl, Abdoulaye Ali Youssouf, Mohammed Mousa
Applied Mathematics, Volume 12, pp 131-146; https://doi.org/10.4236/am.2021.123009

Abstract:
In this paper, we study the positive radial solutions for elliptic systems to the nonlinear BVP: , where Δu = div (∇u) and Δv = div (∇v) are the Laplacian of u, λ is a positive parameter, Ω = {x ∈ Rn : N > 2, |x| > r0, r0 > 0}, let i = [1,2] then Ki :[r0,∞] → (0,∞) is a continuous function such that limr→∞ ki(r) = 0 and is The external natural derivative, and : [0, ∞) → (0, ∞) is a continuous function. We discuss existence and multiplicity results for classes of f with a) fi > 0, b) fi fi = 0. We base our presence and multiple outcomes via the Sub-solutions method. We also discuss some unique findings.
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