Analytical and Numerical Solutions of Pollution Concentration with Uniformly and Exponentially Increasing Forms of Sources

The study of pollution movement is an important basis for solving water quality problems, which is of vital importance in almost every country. This research proposes the motion of flowing pollution by using a mathematical model in one-dimensional advection-dispersion equation which includes terms of decay and enlargement process. We are assuming an added pollutant sources along the river in two cases: uniformly and exponentially increasing terms. The unsteady state analytical solutions are obtained by using the Laplace transformation, and the finite difference technique is utilized for numerical solutions. Solutions are compared by relative error values. The result appears acceptable between the analytical and numerical solutions. Varying the value of the rate of pollutant addition along the river (q) and the arbitrary constant of exponential pollution source term (λ) is displayed to explain the behavior of the incremental concentration. It is shown that the concentration increases as q and λ increase, and the exponentially increasing pollution source is a suitable model for the behavior of incremental pollution along the river. The results are presented and discussed graphically. This work can be applied to other physical situations described by advection-dispersion phenomena which are affected by the increase of those source concentrations.

Piezotronic Effect of a Thin Film With Elastic and Piezoelectric Semiconductor Layers Under a Static Flexural Loading

We theoretically study the electromechanical behaviors of a laminated thin-film piezoelectric semiconductor (PS) composite plate with flexural deformation. The nonlinear equations for drift currents of electrons and holes are linearized for a small carrier concentration perturbation. Following the structural theory systemized by R. D. Mindlin, a system of two-dimensional (2D) equations for the laminated thin-film PS plate, including the lowest order coupled extensional and flexural motion, are presented by expanding the displacement, potential, and the incremental concentration of electrons and holes as power series of the plate thickness. Based on the derived 2D equations, the analytical expressions of the electromechanical fields and distribution of electrons in the thin-film PS plate with an n-type ZnO layer subjected to a static bending are presented. The numerical results show that the electromechanical behaviors and piezotronic effects can be effectively controlled by the external applied force and initial concentration of carriers. The derived 2D equations and numerical results in this paper are helpful for developing piezotronic devices.

The Study of AERMOD and ISCST3 for Area Source Simulation in Taiwan

This research compared the performance of ISCST3 model with the AERMOD simulated for six selected environmental impact assessment (EIA) cases which belongs four kinds of area in Taiwan (hotel, industrial area, road, reservoir). The influence of different terrain (complex or flat) and land use (countryside or urban) was then determined for the two air dispersion models.The results of the cross analysis indicated that there is no significant difference between of the complex terrain and flat terrain on the incremental concentration ratio. However, the biggest difference of incremental concentration of particulate matter (PM) is in the simulation for case in urban (ISCST3 is 1.96 times higher than AERMOD), and the gas pollutants in ISCST3 of incremental concentration simulation results ratio reach to 65.38% more than others. The highest incremental concentration of ISCST3 is 2.67 times to AERMOD. The concentration in AERMOD higher than that in ISTSC3 was 20% in the total 40 simulation values, due to the difference between their vertical diffusion simulations. The ratio of maximum incremental concentration in AERMOD was higher than ISCST3 by 42.5%. By the cross match of these incremental concentration, the ratio that maximum incremental concentration in AERMOD being less than ISCST3 was 22.5% after diffusion, which shows that the sinking rate in AERMOD is faster than ISCST3.The simulation of AERMOD considers more in complex terrain and surface characteristics. It uses the stratified flow over complex terrain and considers the effect in characteristics of the Earth’s surface. Thus, the theoretical basis of AERMOD is solider than ISCST3, and its simulation has more reliability.

Atrial natriuretic peptide: an endogenous factor enhancing sodium excretion in man

1. For many years experimental evidence has suggested the existence of a circulating factor able to enhance sodium excretion. 2. Very recently peptides with natriuretic activity in experimental animals have been isolated from mammalian and human cardiac tissue. In order to determine whether this natriuretic activity has relevance to man we have studied the effects of an infusion of α-human atrial natriuretic peptide (α-h-ANP) in normal subjects. 3. Sodium excretion trebled (P = <0.005) during the infusion of a calculated dose of 15 pmol of α-h-ANP min−1 kg−1 and there was an accompanying diuresis; radioimmunoassay of plasma α-h-ANP during the natriuresis indicated a mean peak incremental concentration of 203 ± 78 (sem) pmol/l. The infusion of a calculated dose of 1.5 pmol min−1 kg−1 did not affect sodium excretion. 4. There were no haemodynamic changes and no side effects were noted.