A study of the power-cosine copula
OMA-Vol. 5 (2021), Issue 1, pp. 85 – 97 Open Access Full-Text PDF
Christophe Chesneau
Abstract: Copulas played a key role in numerous areas of statistics over the last few decades. In this paper, we offer a new kind of trigonometric bivariate copula based on power and cosine functions. We present it via analytical and graphical approaches. We show that it may be used to create a new bivariate normal distribution with interesting shapes. Subsequently, the simplest version of the suggested copula is highlighted. We discuss some of its relationships with the Farlie-Gumbel-Morgensten and simple polynomial-sine copulas, establish that it is a member of a well-known semi-parametric family of copulas, investigate its dependence domains, and show that it has no tail dependence.
Modelling and simulation of a dynamic contact problem in thermo-piezoelectricity
EASL-Vol. 4 (2021), Issue 2, pp. 43 – 52 Open Access Full-Text PDF
Youssef Ouafik
Abstract: In this work, we numerically study a dynamic frictional contact problem between a thermo-piezoelectric body and a conductive foundation. The linear thermo-electro-elastic constitutive law is employed to model the thermo-piezoelectric material. The contact is modelled by the Signorini condition and the friction by the Coulomb law. A frictional heat generation and heat transfer across the contact surface are assumed. The heat exchange coefficient is assumed to depend on contact pressure. Hybrid formulation is introduced, it is a coupled system for the displacement field, the electric potential, the temperature and two Lagrange multipliers. The discrete scheme of the coupled system is introduced based on a finite element method to approximate the spatial variable and an Euler scheme to discretize the time derivate. The thermo-mechanical contact is treated by using an augmented Lagrangian approach. A solution algorithm is discussed and implemented. Numerical simulation results are reported, illustrating the mechanical behavior related to the contact condition.
The incubation periods, the critical immunisation threshold and some other predictors of SARS-CoV-2 disease for different location and different climate countries
EASL-Vol. 4 (2021), Issue 2, pp. 36 – 42 Open Access Full-Text PDF
Marwan Al-Raeei
Abstract: We estimate the incubation period values and other forecasting predictors of SARS-CoV-2 for different countries located in different geographical locations of the earth and each one has a certain climate. The considered countries are the United States, Russia, the United Kingdom, Brazil, Spain, Bahrain, Egypt, Iran, Cyprus, India, France, and the Syrian Arab Republic. For estimating of the forecasting predictors values, we use the SEIR epidemic model and Runge-Kutta simulation method. The estimations are done up to the beginning of 2021 in aforementioned countries based on the collected data in these countries. We find that the incubation period values of SARS-CoV-2 are located between 2.5 days which returns to Bahrain and 10 days which returns to some countries in middle east. Also, we find that the average value of this period is about 6.5 days for the different location countries. Besides, we find that the average values of SARS-CoV-2 critical immunisation threshold, SARS-CoV-2 basic reproduction number and SARS-CoV-2 steady state population are 0.5, 2.3 and 0.5 respectively.
Possibility Pythagorean bipolar fuzzy soft sets and its application
ODAM-Vol. 4 (2021), Issue 2, pp. 17 – 29 Open Access Full-Text PDF
M. Palanikumar, K. Arulmozhi
Abstract: We interact the theory of possibility Pythagorean bipolar fuzzy soft sets, possibility bipolar fuzzy soft sets and define complementation, union, intersection, AND and OR. The possibility Pythagorean bipolar fuzzy soft sets are presented as a generalization of soft sets. Notably, we tend to showed De Morgan’s laws, associate laws and distributive laws that are holds in possibility Pythagorean bipolar fuzzy soft set theory. Also, we advocate an algorithm to solve the decision making problem primarily based on soft set model.
Nirmala energy
ODAM-Vol. 4 (2021), Issue 2, pp. 11 – 16 Open Access Full-Text PDF
Ivan Gutman, Veerabhadrappa R. Kulli
Abstract: A novel vertex-degree-based topological invariant, called Nirmala index, was recently put forward, defined as the sum of the terms \(\sqrt{d(u)+d(v)}\) over all edges \(uv\) of the underlying graph, where \(d(u)\) is the degree of the vertex \(u\). Based on this index, we now introduce the respective “Nirmala matrix”, and consider its spectrum and energy. An interesting finding is that some spectral properties of the Nirmala matrix, including its energy, are related to the first Zagreb index.
On generalization of extended Gegenbauer polynomials of two variables
OMA-Vol. 5 (2021), Issue 1, pp. 76 – 84 Open Access Full-Text PDF
Ahmed Ali Al-Gonah, Ahmed Ali Atash
Abstract: Recently, many extensions of some special functions are defined by using the extended Beta function. In this paper, we introduce a new generalization of extended Gegenbauer polynomials of two variables by using the extended Gamma function. Some properties of these generalized polynomials such as integral representation, recurrence relation and generating functions are obtained.
New-type Hoeffding’s inequalities and application in tail bounds
OMS-Vol. 5 (2021), Issue 1, pp. 248 – 261 Open Access Full-Text PDF
Pingyi Fan
Abstract: It is well known that Hoeffding’s inequality has a lot of applications in the signal and information processing fields. How to improve Hoeffding’s inequality and find the refinements of its applications have always attracted much attentions. An improvement of Hoeffding inequality was recently given by Hertz [1]. Eventhough such an improvement is not so big, it still can be used to update many known results with original Hoeffding’s inequality, especially for Hoeffding-Azuma inequality for martingales. However, the results in original Hoeffding’s inequality and its refined version by Hertz only considered the first order moment of random variables. In this paper, we present a new type of Hoeffding’s inequalities, where the high order moments of random variables are taken into account. It can get some considerable improvements in the tail bounds evaluation compared with the known results. It is expected that the developed new type Hoeffding’s inequalities could get more interesting applications in some related fields that use Hoeffding’s results.
Qualitative analysis of solutions for a parabolic type Kirchhoff equation with logarithmic nonlinearity
ODAM-Vol. 4 (2021), Issue 2, pp. 1 – 10 Open Access Full-Text PDF
Erhan Pişkin, Tuğrul Cömert
Abstract: In this work, we investigate the initial boundary-value problem for a parabolic type Kirchhoff equation with logarithmic nonlinearity. We get the existence of global weak solution, by the potential wells method and energy method. Also, we get results of the decay and finite time blow up of the weak solutions.
A hybrid method for solution of linear Volterra integro-differential equations (LVIDES) via finite difference and Simpson’s numerical methods (FDSM)
OMA-Vol. 5 (2021), Issue 1, pp. 69 – 75 Open Access Full-Text PDF
Bashir Danladi Garba, Sirajo Lawan Bichi
Abstract: In this paper, a hybrid of Finite difference-Simpson’s approach was applied to solve linear Volterra integro-differential equations. The method works efficiently great by reducing the problem into a system of linear algebraic equations. The numerical results shows the simplicity and effectiveness of the method, error estimation of the method is provided which shows that the method is of second order convergence.
Trinomial equation: the Hypergeometric way
OMS-Vol. 5 (2021), Issue 1, pp. 236 – 247 Open Access Full-Text PDF
Daniele Ritelli, Giulia Spaletta
Abstract: This paper is devoted to the analytical treatment of trinomial equations of the form \(y^n+y=x,\) where \(y\) is the unknown and \(x\in\mathbb{C}\) is a free parameter. It is well-known that, for degree \(n\geq 5,\) algebraic equations cannot be solved by radicals; nevertheless, roots are described in terms of univariate hypergeometric or elliptic functions. This classical piece of research was founded by Hermite, Kronecker, Birkeland, Mellin and Brioschi, and continued by many other Authors. The approach mostly adopted in recent and less recent papers on this subject (see [1,2] for example) requires the use of power series, following the seminal work of Lagrange [3]. Our intent is to revisit the trinomial equation solvers proposed by the Italian mathematician Davide Besso in the late nineteenth century, in consideration of the fact that, by exploiting computer algebra, these methods take on an applicative and not purely theoretical relevance.