Search results

The purpose of this paper is to examine cigarette consumption behavior of younger cohorts in the urban and rural areas of Iran. The authors use Iran’s annual Household Income and Expenditures Surveys (HIES) database over 2007–2013 for the statistical analysis. In order to control for a large number of households with zero expenditure on cigarette consumption, the authors have used the double-hurdle modeling approach for counting the outcomes of interest. The authors have also limited the sample to cases in which the head of household is between the ages of 21 and 45 and all children are younger than 18.

In this study, the authors have conducted a multivariate econometric analysis to identify the impact of age and birth year cohort on the demand for cigarettes among Iranian households. The authors have used the HIES data for multiple years in the analysis. The ideal data set for the analysis is a panel data that include information on cigarette consumption of various age cohorts over a long period of time. Since no suitable panel data are available, the authors have constructed a multi-year cohort data by extracting cohort data from the annual HIES data set. Due to the unique properties of cigarette consumption, the authors have used the double-hurdle econometric model with appropriate diagnostics.

After controlling for price and demographic factors, which affect the demand for cigarettes, the authors find that the younger cohorts in rural areas, who smoke, tend to consume fewer cigarettes than the older ones; however, the opposite is true among urban households. The probability of being a non-smoker is larger for younger cohorts in both rural and urban areas. Among smokers, the authors observe an inverse U-shape relation between age and quantity of cigarettes consumed per day. The trend is positive up to age 45, but diminishes for older smokers because of health concerns.

In comparison to previous studies of tobacco consumption in Iran, the authors have used a more comprehensive household income and expenditure survey data set with a large number of observations. Furthermore, the authors have applied an econometric method (the double-hurdle model), which is suitable for the analysis of the determinants of demand for cigarettes when a subset of households report no cigarette consumption.

Although many studies have been conducted on the nanofluid flow in microtubes, this paper, for the first time, aims to investigate the effects of nanoparticle diameter and concentration on the velocity and temperature fields of turbulent non-Newtonian Carboxymethylcellulose (CMC)/copper oxide (CuO) nanofluid in a three-dimensional microtube. Modeling has been done using low- and high-Reynolds turbulent models. CMC/CuO was modeled using power law non-Newtonian model. The authors obtained interesting results, which can be helpful for engineers and researchers that work on cooling of electronic devices such as LED, VLSI circuits and MEMS, as well as similar devices.

Present numerical simulation was performed with finite volume method. For obtaining higher accuracy in the numerical solving procedure, second-order upwind discretization and SIMPLEC algorithm were used. For all Reynolds numbers and volume fractions, a maximum residual of 10⁻⁶ is considered for saving computer memory usage and the time for the numerical solving procedure.

In constant Reynolds number and by decreasing the diameter of nanoparticles, the convection heat transfer coefficient increases. In Reynolds numbers of 2,500, 4,500 and 6,000, using nanoparticles with the diameter of 25 nm compared with 50 nm causes 0.34 per cent enhancement of convection heat transfer coefficient and Nusselt number. Also, in Reynolds number of 2,500, by increasing the concentration of nanoparticles with the diameter of 25 nm from 0.5 to 1 per cent, the average Nusselt number increases by almost 0.1 per cent. Similarly, In Reynolds numbers of 4,500 and 6,000, the average Nusselt number increases by 1.8 per cent.

The numerical simulation was carried out for three nanoparticle diameters of 25, 50 and 100 nm with three Reynolds numbers of 2,500, 4,500 and 6,000. Constant heat flux is on the channel, and the inlet fluid becomes heated and exists from it.

The authors obtained interesting results, which can be helpful for engineers and researchers that work on cooling of electronic devices such as LED, VLSI circuits and MEMS, as well as similar devices.

This manuscript is an original work, has not been published and is not under consideration for publication elsewhere. About the competing interests, the authors declare that they have no competing interests.