Sandpiles Subjected to Sinusoidal Drive

This paper considers a sandpile model subjected to a sinusoidal external drive with the time period $T$. We develop a theoretical model for the Green function in a large $T$ limit, which predicts that the avalanches are anisotropic and elongated in the oscillation direction. We track the problem numerically and show that the system shows additionally a regime where the avalanches are elongated in the perpendicular direction with respect to the oscillations. We find a transition point between these two regimes. The power spectrum of avalanche size and the grains wasted from the parallel and perpendicular directions are studied. These functions show power-law behaviour in terms of the frequency with exponents, which run with $T$

Pushmepullyou: An efficient micro-swimmer

The swimming of a pair of spherical bladders that change their volumes and mutual distance is efficient at low Reynolds numbers and is superior to other models of artificial swimmers. The change of shape resembles the wriggling motion known as {\it metaboly} of certain protozoa.Comment: Minor rephrasing and changes in style; short explanations adde

Proposal for a standard problem for micromagnetic simulations including spin-transfer torque

The spin-transfer torque between itinerant electrons and the magnetization in a ferromagnet is of fundamental interest for the applied physics community. To investigate the spin-transfer torque, powerful simulation tools are mandatory. We propose a micromagnetic standard problem includingthe spin-transfer torque that can be used for the validation and falsication of micromagnetic simulation tools. The work is based on the micromagnetic model extended by the spin-transfer torque in continuously varying magnetizations as proposed by Zhang and Li. The standard problem geometry is a permalloy cuboid of 100 nm edge length and 10 nm thickness, which contains a Landau pattern with a vortex in the center of the structure. A spin-polarized dc current density of 1012 A/m2 flows laterally through the cuboid and moves the vortex core to a new steady-state position. We show that the new vortex-core position is a sensitive measure for the correctness of micromagnetic simulatorsthat include the spin-transfer torque. The suitability of the proposed problem as a standard problem is tested by numerical results from four different finite-difference and finite-element-based simulation tools

The role of effective information in decision making by managers at Shahid Beheshti of teaching hospitals of Shahid Beheshti university of medical sciences

Today, one of the most fundamental factors in the field of management is providing managers with effective information in order to improve the quality of their decision-making. In this paper, we studied the role of effective information in decision making by managers and directors in 2006- 2007(From March 20, 2006 to march 19, 2007)

(Non)Equilibrium of OH and Differential Transport in MILD Combustion:Measured and Computed OH Fractions in a Laminar Methane/Nitrogen Jet in Hot Coflow

Spatial distributions of temperature, major species, and OH mole fractions under moderate or intense low-oxygen-dilution (MILD) conditions in a laminar-jet-in-hot-coflow configuration were measured using spontaneous Raman and laser-induced-fluorescence methods. A preheated mixture of 18% CH4/82% N2 at 1100 K was used as fuel, while the products of a laminar, flat, premixed burner-stabilized flame with an equivalence ratio of 0.8 at 1550 K were used as the oxidizer. For comparison, experiments replacing the fuel by pure N2 were also performed. The measurements are compared with the results of numerical simulations performed using the GRI-Mech 3.0 chemical mechanism and a multicomponent mixture-averaged transport model. Analysis of the data shows that the maximum axial and radial temperature and OH mole fraction occur on the lean side of the stoichiometric mixture fraction. MILD combustion generates maximum OH mole fractions of ∼700 ppm in the radial profiles close to the burner exit and ∼300 ppm along the centerline, more than five times lower than those measured in equivalent methane/air diffusion flames. Overall, good qualitative and quantitative agreement is found between the results of detailed computations and experiments, with the maximum differences observed in the axial OH profiles, which are just outside the estimated experimental uncertainty. Analysis of the computational results shows that differential diffusion hinders the use of the mixture fraction to estimate the equilibrium temperature and species fractions, causing an overestimation of the stoichiometric temperature by ∼200 K. Calculating the equilibrium quantities based on the local (computed) species fractions shows an axial temperature profile that differs from that experimentally/computationally determined by less than 25 K. The analysis further shows that the measured OH mole fractions are roughly three times higher than the (locally determined) equilibrium value