مجله بین المللی محاسبات و مدل سازی ریاضی
سال دهم شماره 2 (Spring 2020)

Traditional Data Envelopment Analysis (DEA) models evaluate the efficiency of decision making units (DMUs) with common crisp input and output data. However, the data in real applications are often imprecise or ambiguous. This paper transforms fuzzy fractional DEA model constructed using fuzzy arithmetic, into the conventional crisp model. This transformation is performed considering the goal programming that is one of the Multi Objective Programming (MOP) methods. Therefore, in this research the one linear programming model measures the fuzzy efficiencies of DMUs with fuzzy input and fuzzy output data.

This study is carried out to describe the behaviour of vehicles flow on the road, in the presence of blocking effects. A non-linear three dimensional system of ordinary differential equations is used to describe vehicles flow on the road. The study classify total vehicles population on the road into three compartments as Free – Slow – Released vehicles. The formulated model is well-posed. The blocking free equilibrium point is globally asymptotically stable. Further, effects of blocking are described using concept of retardation number. That is, blocking effect decrease whenever retardation number is less than one and the blocking effects increase if retardation number is greater than one.

In this paper, we have obtained and presented new relativistic stellar configurations considering an anisotropic fluid distribution with a charge distribution and a gravitational potential Z(x) that depends on an adjustable parameter. The quadratic equation of state based on Feroze and Siddiqui viewpoint is used for the matter distribution. The new solutions can be written in terms of elementary and polynomial functions. We have investigated that the radial pressure, metric coefficients, energy density, anisotropy factor, charge density, mass function have been well defined and are regular in the interior of these new models, which satisfy all physical properties in a realistic star.

The consequences of Maternal Mortality (MM) cannot be overemphasized. It inhibits population growth resulting into loss of lives among others. This work tends to obtain the maternal mortality rates (MMR) in Nigeria, identify some fitted distributions to MMR and determine which of the distributions best fits the data. A comprehensive Exploratory Data Analysis (EDA) was carried on MM and the MMRs were obtained. Two parameters Gamma distribution, Weibull and Exponential distributions were fitted for MM. Both BIC and AIC selection criteria were adopted in selecting the most fitted distribution. The AIC for Gamma, Weibull and Exponential distributions fitted for MMR were 1339.396, 1340.161 and 370.5244 respectively. Also, the BIC for Gamma, Weibull and Exponential distributions fitted for MM were 1344.971, 1345.736 and 373.3119 respectively. It can be observed that Exponential distribution has the least AIC (370.5244) and least BIC (373.3119), therefore, it is the most fitted distribution for MM. The estimate (standard error) of exponential distribution on MM is 0.5853 indicating the fitness of the distribution being the one with the least error. Conclusively, the model obtained from this study can be used to study and monitor MM in Nigeria to achieve a better economy and thus brings about local and national development.

The emergence of corona virus (COVID-19) has create a great public concern as the outbreak is still ongoing and government are taking actions such as holiday extension, travel restriction, temporary closure of public work place, borders, schools, quarantine/isolation, social distancing and so on. To mitigate the spread, we proposed and analyzed a stochastic model for the continue spread of corona virus (COVID-19) dynamics considering the impact of vaccination among susceptible, exposed and quarantine cases. The difference and differential-difference equations for the dynamics of (COVID-19) were derived and simulated with available parameters using stochastic simulation (Gillespie Algorithm). The study adopts Continues–Time Birth and Death stochastic process and the probability distribution describing the dynamics of coronavirus was derived and simulated which shows an exponential decay over time. As the time increase, the probability of coronavirus incidents decline to zero. We therefore conclude that vaccination has an impact of 20% among susceptible, exposed and quarantine cases.

In this paper, we formulated a dynamical model of COVID-19 to describe the transmission dynamics of the disease. The well possedness of the formulated model equations was proved. Both local and global stability of the disease free equilibrium and endemic equilibrium point of the model equation was established using basic reproduction number. The results show that, if the basic reproduction number is less than one then the solution converges to the disease free steady state i.e. the disease free equilibrium is asymptotically stable. The endemic states are considered to exist when the basic reproduction number for each disease is greater than one. Numerical simulation carried out on the model revealed that an increase in level of contact rate among individuals has an effect on reducing the prevalence of COVID-19 and COVID-19 disease. Furthermore, sensitivity analysis of the model equation was performed on the key parameters to find out their relative significance and potential impact on the transmission dynamics of COVID-19.