a numerical model for simulating residence time distribution (rtd) of turbulent flows in helical static mixers is proposed and developed to improve the understanding of static mixers. the results of this model is presented in terms of different volumetric flow rate to illustrate the complicated flow patterns that drive the mixing process in helical static mixers. the computed results are also u...

This paper presents an analytical model characterizing unsteady groundwater flow in an unconfined aquifer resting on a sloping impervious bed. The aquifer is in contact with a constant water level at one end. The other end is connected to a stream whose level is increasing form an initial level to a final level at a known exponentially decaying function of time. Moreover, the aquifer is repleni...

In this paper, using sub-supersolution argument, we prove an existence result on positive solution for an ecological model under certain conditions. It also describes the dynamics of the fish population with natural predation and constant yield harvesting. The assumptions are that the ecosystem is spatially homogeneous and the herbivore density is a constant which are valid assumptions for mana...

A locus equation describes a 1st order regression fit to a scatter of vowel steady-state frequency values predicting vowel onset frequency values. Locus equation coefficients are often interpreted as indices of coarticulation. Speaking rate variations with a constant consonant-vowel form are thought to induce changes in the degree of coarticulation. In the current work, the hypothesis that locu...

abstract t his paper explains bilateral trade patterns between south korea and thirteen opec member countries over the period 1980-2014 using a gravity model. the estimation results show that the gravity equation fits the data reasonably well. we confirmed the existence of long term relationships between the bilateral trade flows and the main components of gravity model - gdp, income (gdp per c...

BACKGROUND Valve areas derived by the Gorlin formula have been observed to vary with transvalvular volume flow rate. Continuity equation valve areas calculated from Doppler-echo data have become a widely used alternate index of stenosis severity, but it is unclear whether continuity equation valve areas also vary with volume flow rate. This study was designed to investigate the effects of chang...

the effect on sugar beets of water and nitrogen movement in the soil under different water conditions was assessed over two years (2000-1) at the khorasan agricultural research center. three water treatments (no water stress, continuous stress and primary stress) and three n amounts (80, 160 and 240 kg n/ha) were investigated. the amount of moisture depletion in the water treatments was 50%, 80...

We further develop the general theory of the area reactivity model that provides an alternative description of the diffusion-influenced reaction of an isolated receptor-ligand pair in terms of a generalized Feynman-Kac equation. We analyze both the irreversible and reversible reaction and derive the equation of motion for the survival and separation probability. Furthermore, we discuss the noti...