SUMMARYThe interaction of a tunnel-soil-building system due to trains is investigated by a substructure technnique. The soil medium is assumed to be a viscoelastic halfspace. The method of wave function expansion is used to construct the displacement fields in terms of potentials. The total soil-structure interaction problem is decomposed into a foundation radiation problem and a tunnel radiation problem. The impedance matrices for the corresponding substructure problems are obtained using a collocation technique. The steady state response of buildings for a given tunnel-foundation geometry is determined using the impedance matrix. Hence, the response of the building to train loading at different speeds is evaluated and compared with allowable vibration limits.
Two-dimensional (2D) semiconductors with point defects
are predicted
to host a variety of bound exciton complexes analogous to trions and
biexcitons due to strong many-body effects. However, despite the common
observation of defect-mediated subgap emission, the existence of such
complexes remains elusive. Here, we report the observation of bound
exciton (BX) complex manifolds in monolayer MoSe2 with
intentionally created monoselenium vacancies (VSe) using
proton beam irradiation. The emission intensity of different BX peaks
is found to exhibit contrasting dependence on electrostatic doping
near the onset of free electron injection. The observed trend is consistent
with the model in which free excitons exist in equilibrium with excitons
bound to neutral and charged VSe defects, which act as
deep acceptors. These complexes are more strongly bound than trions
and biexcitons, surviving up to around 180 K, and exhibit moderate
valley polarization memory, indicating partial free exciton character.
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