Wrocław University of Technology

About: Wrocław University of Technology is a education organization based out in Wrocław, Poland. It is known for research contribution in the topics: Laser & Fuzzy logic. The organization has 13115 authors who have published 31279 publications receiving 338694 citations.

Equivalence of the fractional Fokker-Planck and subordinated Langevin equations: the case of a time-dependent force.

Abstract: A century after the celebrated Langevin paper [C.R. Seances Acad. Sci. 146, 530 (1908)] we study a Langevin-type approach to subdiffusion in the presence of time-dependent force fields. Using a subordination technique, we construct rigorously a stochastic Langevin process, whose probability density function is equal to the solution of the fractional Fokker-Planck equation with a time-dependent force. Our model provides physical insight into the nature of the corresponding process through the simulated trajectories. Moreover, the subordinated Langevin equation allows us to study subdiffusive dynamics both analytically and numerically via Monte Carlo methods.

Effect of asphaltenes on hydroprocessing of heavy oils and residua

Abstract: Asphaltenes raise trouble in petroleum processing. During the hydroprocessing of heavy feedstock, asphaltenes limit the efficiency of conversion and refining, act as coke precursors leading to catalyst deactivation. The effect of asphaltenes and their solubility in oil on the formation of solids have been extensively studied in the last decades. In this paper, the state of the art is reviewed, covering the changes in the chemical structure of asphaltenes upon hydrotreatment, leading to the reduction in product stability. As a result, asphaltenes might precipitate, causing coke deposition on the catalyst and the formation of deposits in the refinery equipment. This is the main reason for the limitation of conversion resulting in the reduction in the product yield.