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   At this study, effect of paddy drying method with three levels (shadow drying, sun drying and oven drying), paddy grain moisture content at four levels (8, 10, 12, 14 w.b.%) and common paddy varieties in Guilan province  at three levels (Hasani, Hashemi and Alikazemi) were investigated  on broken grains percent duo to milling process.   The results that breakage percent of grains was least at tests with shad drying method. The mean highest breakage percent of grains at husking stage (14.061%) was obtained at tests with Hashemi variety and oven drying method. The mean least breakage percent of grains at husking stage (5.351%) was obtained at tests with Alikazemi variety and shad drying method. With increasing of grain moisture content of milling from 8 to 14 w.b. %, breakage percent of grains at husking and whitening stages were decreased from 11.616 % to 7.717 % and 21.025 to 12.841%, respectively. The mean highest (21.340%) and least (13.841%) breakage of grain whitening obtained at tests with sun drying and shad drying methods, respectively. The mean highest (20.539) and least (14.150%) breakage percent of grain whitening obtained at tests with Hasani and Hashemi and Alikazemi varieties, respectively.

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In this study, effects of zeta potential distribution and geometrical specifications are numerically investigated on mixing efficiency in electroosmotic flows. Considered geometries include straight, converging, diverging, and converging-diverging microchannels. Electroosmotic flow simulations are conducted based on the N-S and Nernst-Planck equations for momentum and ionic charges distributions, respectively, by lattice Boltzmann method. Numerical simulations are validated against available analytic electroosmotic flow solutions in homogeneous straight channels, and then flow patterns and mixing performances in the presence of non-uniform zeta potential distributions are investigated in search for enhanced mixing performances. Numerical results indicate that converging channel leads to a sizable increase in mixing efficiencies, while the flow rate decreases at the same time. In contrast, diverging channels increase the flow rate, while decrease the mixing efficiency. Therefore, it is expected to achieve a balance between the mixing efficiency and mass flow rate using converging-diverging geometries. Numerical results indicate that mixing efficiency of about 90% can be reached with a converging-diverging microchannel with a reasonable decrease in mass flow rate as compared to its geometrical diverging-converging counterpart channel.

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In this paper, switching process of electro osmotic flow is numerically and analytically investigated in a two dimensional Y-shape three-way channel. In this research, it is shown that changing the flow direction through a three-way channel can be simply conducted by varying applied electrical voltage at channel’s ends. In theoretical approach, three equations are introduced to approximate switching voltage ratio and dimensionless flow rate before and after switching process, respectively. These equations are derived base on some simplifying assumptions when distance between output branches and dimensionless double layer thickness parameter are assumed to be flow variables. Numerical simulations are also conducted by using the lattice Boltzmann method to solve all governing equations including the Navier - Stokes, the Poisson - Boltzmann, and the Laplace equations in a 2D three-way channel geometry. Comparison between analytical and numerical results indicates that introduced approximated equations can successfully predict switching voltage ratio and dimensionless flow rate (before and after switching process) by employing considerably lower computational efforts in comparison with numerical approach. In this regard, the introduced semi-analytical equations can be useful for better understanding and to more effectively designing of micro electro mechanics systems.

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In this study, effects of zeta potential distribution and geometrical specifications are investigated on mixing efficiency in electroosmotic flows. Flow geometry in this research is a series of converging-diverging microchannels with different diverging ratios. Governing equations including the Navier Stokes equation for fluid flow and the Poisson-Boltzmann equation for internal electrical field are solved numerically in a two-dimensional domain by using the lattice Boltzmann method. Numerical simulations are validated against available analytic solutions for electroosmotic flow in homogeneous straight channels. The response surface methodology (RSM) is then employed to investigate relationship between flow variables and consequently to optimize mixing efficiency and flow rate of the channel. Results indicate that increasing the zeta potential ratio and diverging ratio, leads to increased value of flow rate, while meanwhile it decreases the mixing efficiency. Zeta potential pattern does not affect flow rate considerably, but its effects on mixing efficiency is noticeable. Furthermore, it is found that mixing efficiency and flow rate are more sensitive to zeta potential ratio than diverging ratio. At last, optimum parameters are determined by RSM which are 0.5 for zeta potential ratio, 0.6 for diverging height, and pp-nn pattern for zeta potential distribution, all associated to simultaneously maximized flow rate and mixing efficiency.

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Maximum temperatures affect a wide range of activities especially in the afternoon hours and warm period of the year. This paper analyses temporal and spatial variations of mean maximum temperatures and the highest temperatures in Iran by using the statistical methods within a 45-year period (1964 to 2008). Temperature zonings were performed by using raster GIS capabilities, and evaluated by various statistical tests. Also the relationships between maximum temperatures and geographical factors, as well as temperature trends, were investigated via regression equations. The results of the study revealed six different zones of maximum temperatures in Iran. Analysis of the maps and comparison of the standardized β coefficients of multivariate regression models, confirms the latitude and then the altitude significant roles in controlling the maximum temperatures, especially during the cold period of the year, along with the lowest temperature variabilities in the southern coasts. Shapiro-Wilk and Levene tests indicated respectively normality of the temperatures and in most cases equality of temperature variances between zones. Also Games-Howell and Gabriel tests proved that the mean maximum temperatures among the zones have significant pairwise differences in all time scales that prove the accuracy of the zonings. Mean afternoon temperature over the country was calculated based on raster calculations at the rate of 25.3○C, which has been increased at the rate of 0.62○C compared to the last 45 years.