First principle study of the thermal conductance in graphene nanoribbon with vacancy and substitutional silicon defect

The thermal conductance in graphene nanoribbon with a vacancy or silicon point defect (substitution of C by Si atom) is investigated by non-equilibrium Green's function (NEGF) formalism combined with first-principle calculations density-functional theory with local density approximation. An efficient correction to the force constant matrix is presented to solve the conflict between the long-range character of the {\it ab initio} approach and the first-nearest-neighboring character of the NEGF scheme. In nanoribbon with a vacancy defect, the thermal conductance is very sensitive to the position of the vacancy defect. A vacancy defect situated at the center of the nanoribbon generates a saddle-like surface, which greatly reduces the thermal conductance by strong scattering to all phonon modes; while an edge vacancy defect only results in a further reconstruction of the edge and slightly reduces the thermal conductance. For the Si defect, the position of the defect plays no role for the value of the thermal conductance, since the defective region is limited within a narrow area around the defect center.Comment: accepted by AP

Dynamics of the Changjiang River Plume

The extension of the Changjiang River plume is one of the fundamental processes in the Yellow and East China Seas, which is responsible not only for the physical properties of seawater but also for the numerous physical, biogeochemical, and sedimentary processes in this region. The studies of the Changjiang River plume dated back to 1960s, followed by generations, and are still attracting numerous focuses nowadays. Here in this chapter, we will review the past studies on the Changjiang River plume and present some latest studies on this massive river plume. The latest research progresses on the Changjiang River plume are mainly related to the tidal modulation mechanisms. It is found that the tide shifts the Changjiang Rive plume to the northeast outside the river mouth, bifurcates the plume at the head of submarine canyon, and arrests the unreal up-shelf plume intrusion that occurred frequently in previous model studies. It is also found that the tidal residual current transports part of the Changjiang River plume to the Subei Coastal Water. These tidal modulation effects can answer the questions on the dynamics of Changjiang River plume that puzzled the research community for decades