Using the π-band tight-binding (TB) model and the quantum box boundary condition, we have discussed how both of the applied strain and finite-length affect the energy bands of metallic carbon nanotubes (CNTs). It is found that, for finite-length CNTs, energy gap for the armchair tube under...

We investigate the effects of constraining leverage and shrinking covariance matrix in constructing large portfolios, both theoretically and empirically. Considering a wide variety of setups that involve conditioning or not conditioning the covariance matrix estimator on the recent past...

Grazing exclusion has been used extensively in alpine meadows of the Tibetan Plateau. However, in recent years, studies have shown a decreasing trend in soil nutrients because of grazing exclusion and climate change. The effects of grazing exclusion on the soil biogeochemical process of...