Role Of Edge Effects Research Articles

Role of edge effects and fluid depth in azimuthal Faraday waves

Faraday waves are created in experiment with spatial structure that conforms to the cylindrical container geometry and is defined by the mode number pair ($n,\ensuremath{\ell}$). The shape of the instability tongue in the frequency-acceleration space depends upon the edge conditions, filling depth, and liquid properties.

Experimental study of the magnetic characteristics of nanocrystalline thin films: the role of edge effects

Magnetic characteristics and their spatial distribution of magnetron sputtered nanocrystalline NiFe thin films of various compositions were investigated by ferromagnetic resonance (FMR) and magneto-optical Kerr effect microscopy. A sharp increase in the FMR linewidth and a strong deviation of the uniaxial magnetic anisotropy field were observed near the film edges. It was shown that the observed magnetic anisotropy behavior can be explained by assuming that besides the field-induced uniaxial magnetic anisotropy an additional source of the uniaxial anisotropy near the film edges exists, with the easy axis parallel to the edges. The possible origins of this additional contribution were discussed.

Determination of the role of edge effects in Lennard-Jones fluid adsorption in finite slits by computer simulation

Lennard-Jones fluid adsorption in bounded slits has been calculated by the Monte Carlo method. Isotherms of methane adsorption in circular finite carbon slits with different widths have been calculated in a wide pressure range. For finite slits, the contribution of edge effects to the adsorption behavior of methane has been estimated as compared with infinite slits. Qualitative agreement with the conclusions of the asymptotic theory has been reached for the behavior of local density in finite slits.

Stemflow acid neutralization capacity in a broadleaved deciduous forest: The role of edge effects

Atmospheric deposition is an important pathway for moisture, nutrient, and pollutant exchange among the atmosphere, forest, and soils. Previous work has shown the importance of proximity to the forest edge to chemical fluxes in throughfall, but far less research has considered stemflow. This study examined the difference in acid neutralization capacity (ANC) of stemflow of nineteen Liriodendron tulipifera L. (yellow poplar) trees between the forest edge and interior in a rural area of northeastern Maryland. We measured ANC directly via potentiometric titration. Stemflow from trees at the forest edge was found to have significantly higher and more variable pH and ANC than in the forest interior (p < 0.01). No mathematical trend between ANC and distance to the forest edge was observed, indicating the importance of individual tree characteristics in stemflow production and chemistry. These results reaffirm the importance of stemflow for acid neutralization by deciduous tree species.

Effect of screening on the emissivity of field electron emitters based on carbon nanotubes

The effect of screening on the emissivity of a field cathode built around a carbon nanotube array is analyzed. A numerical method of solving the Laplace equation for intricate-shape cathodes is developed that makes it possible to relate the amplification factor to the nanotube spacing in arrays containing as many as 225 emitters. Mutual screening of the tubes, which shows up in the dependence of the field amplification factor on the average emitter spacing, is studied numerically. The optimal spacing between the tubes that provides an emission current maximum density at a given applied voltage is determined. The role of edge effects in carbon nanotube screening is established.

Importance of electrode conductive surface area and edge effects on ventricular defibrillation efficacy.

The role of edge effects and electrode surface area of the right ventricular (RV) transvenous lead (TVL) on defibrillation efficacy is unknown. Defibrillation threshold (DFT) testing was conducted randomly in 12 dogs using ring electrode leads in an RV/SVC (superior vena cava) or RV/SVC/patch system. The leads (RV-4, RV-8t, RV-8, RV-15) had electrode surface areas of 20%, 20%, 40%, and 70%, respectively. A computer model predicted the magnitude of electrode surface current (RV-8t > RV-4 > RV-8 > RV-15) and the potential distribution (PD) at four sites: electrode surface (site a) and at 2 mm (b), 4 mm (c), and 8 mm (d) away from the surface. Despite different near-field PDs (sites a, b, c), PDs were nearly identical at site d. Resistance decreased as the surface area increased. DFT energy for the RV-15 lead was lower than the RV-4 and RV-8t. There was no difference between energy requirements for the RV-15 and RV-8 leads. No difference was found in DFT current for each lead. Comparison of the RV-8t and RV-4 leads showed no difference in DFT energy despite a lower resistance and a greater number of edges. Increasing the RV TVL surface area lowered the resistance. However, surface area coverages > or = 40% did not lower DFT energy. No significant change in DFT current occurred despite different predicted near-field current densities. PDs were nearly identical 8 mm from the electrode surface. Thus, the far-field current density appears to play a more important role in determining defibrillation success.

An Efficient 2D Finite Element Procedure for the Quenching Analysis With Phase Change

An efficient finite element procedure has been developed for the analysis of quenching problems involving nonisothermal phase changes. The finite element analysis includes temperature dependent material properties, a mixed hardening rule to describe the material constitutive model, and the incorporation of time-temperature-transformation (TTT) diagrams. The procedure is applied to the simulation of quenching of steel cylinders and an aluminum connector with temperature-dependent convection boundary conditions. First, the stress analysis of the quenching of an infinite cylinder is carried out and the predicted distributions of temperature and stresses are compared with an available numerical solution to validate the accuracy of the present formulation and procedure. To demonstrate the predictive capability and practical applicability of the developed procedure, the simulation of quenching of finite cylinders of various length-to-diameter ratios and of a square bar are presented. The role of edge effects and specimen geometry on the residual stress distribution is analyzed. In addition, the microstructures developed during the quenching of 1080 carbon steel cylinders are predicted using TTT diagram incorporated in the analysis. The final example addresses the simulation of age hardening in spray quenched 2024 aluminum connector. The example problems are directly related to many practical applications, such as the heat-treatment of solid piston pins used in automotive engines and the spray quenching of aluminum connector. They also illustrate the wide range of material transformations which can be modeled using the present finite element procedure.