The consequences of nuclear black holes for the structure and dynamics of stellar spheroids are reviewed. Slow growth of a black hole in a pre-existing core produces a power-law cusp, ρ ∼ r −γ , with γ ≈ 2, similar to the steep cusps seen in faint elliptical galaxies. The weaker cusps in bright ellipticals, γ ∼ < 1, may result from ejection of stars by a coalescing black-hole binary; there is m...

We discuss an analytic approach for modeling structure formation in sheets, filaments and knots. This is accomplished by combining models of triaxial collapse with the excursion set approach: sheets are defined as objects which have collapsed along only one axis, filaments have collapsed along two axes, and halos are objects in which triaxial collapse is complete. In the simplest version of thi...

We discuss an analytic approach for modeling structure formation in sheets, filaments and knots. This is accomplished by combining models of triaxial collapse with the excursion set approach: sheets are defined as objects which have collapsed along only one axis, filaments have collapsed along two axes, and halos are objects in which triaxial collapse is complete. In the simplest version of thi...

[1] Understanding the mechanical behavior of rock is critical for researchers and decision-makers in fields from petroleum recovery to hazardous waste disposal. Traditional continuum-based numerical models are hampered by inadequate constitutive relationships governing fracture initiation and growth. To overcome limits associated with continuum models we employed a discrete model based on the f...

nowadays acoustic emission (ae) testing based on the kaiser effect (ke) is increasingly used to estimate the in-situ stress in laboratories. in this work, this effect is assessed on cylindrical specimens in numerical simulations of the cyclic loadings including loading, unloading, and re-loading cycles using a 3d code called the particle flow code (pfc) based upon the distinct element method. t...

Ballast, typically comprising large sized aggregate particles with uniform gradation, is an essential layer in the railroad track substructure. Functions of ballast include facilitating load distribution and drainage, maintaining track geometry and track stability, and providing track resilience and noise absorption. Throughout its service life, ballast goes through changes in gradation and par...