Wyniki wyszukiwania - BazTech

Ograniczanie wyników

Znaleziono wyników: 2

Liczba wyników na stronie

Wyniki wyszukiwania

Sortuj według:

Ogranicz wyniki do:

Effective elastic properties and pressure distribution in bidisperse granular packings: DEM simulations and experiment

Wiącek J., Stasiak M., Parafiniuk P.

Archives of Civil and Mechanical Engineering

2017

Vol. 17, no. 2

271--280

The effective elastic properties and pressure distribution in granular mixtures depend on both, material and geometric properties of particles. Using the discrete element method, the effect of geometric and statistical factors on the mechanical response of binary packings of steel beads under uniaxial confined compression was studied. The ratio of the diameter of small and large spheres in bidisperse mixtures was chosen to prevent small particles from percolating through bedding. The study addressed lateral-to-vertical pressure ratio and effective elastic modulus of particulate beds. The bimodality of mixtures was found to have a strong effect on the packing density of samples with the ratio between large and small particles larger than 1.3; however, no effect of particle size ratio and contribution of particle size fractions on the distribution of pressure and elasticity of bidisperse packings was observed. Regardless on the composition of mixtures, the lateral-to-vertical pressure ratio followed the same paths with increasing contribution of small particles in mixtures. The effective elastic modulus of granular packings increased with increasing compressive load and was slightly affected by geometric and statistical factors. The experimental data followed the same trend of the DEM predictions; however, only qualitative agreement between numerical and experimental results was obtained. The discrete element method generated packings with smaller density and overpredicted pressure ratios and elastic parameters of mixtures.

Transient effects in electron transport through quantum dots

Wiertel M., Parafiniuk P., Taranko R.

Optica Applicata

2009

Vol. 39, nr 4

959-965

We investigate the transient electron transport through the quantum dot and double quantum dot systems coupled with the time-dependent barriers to infinitely large reservoirs of noninteracting electrons. Time-dependent currents and quantum dot occupancies are calculated using both nonequilibrium Green's functions formalism and the equation of motion method for appropriate correlation functions. We show that the sequence of ultrafast modulation of the tunneling amplitudes between the electron reservoirs and the quantum dots can induce quite different electron occupation of the quantum dot in comparison with the static case. We also find that the oscillations of the transient current following the sudden coupling of the electron reservoirs with the double quantum dot system have the same frequency as Rabi's oscillations of the double dot state vector.transient current.