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An optical nanoantenna consisting of a Au-dielectric core-shell nanocube dimer with switchable directionality was designed and described. Our theoretical model and numerical simulation showed that switching between forward and backward directions can be achieved with balanced gain and loss, using a single element by changing the coefficient κ in the core, which can be defined by the relative phase of the polarizability. The optical response indicated a remarkable dependence on the coefficient κ in the core as well as frequency. The location of the electric field enhancement was specified by the different coefficient κ and, furthermore, the chained optical nanoantenna and coupled electric dipole emitted to the optical nanoantenna played significant roles in unidirectional scattering. This simple method to calculate the feasibility of unidirectional and switchable scattering provides an effective strategy to explore the functionalities of nanophotonic devices.

We propose a multilayered metal-dielectric nanoantennas with PT symmetiy for tailoring electric dipole emission. It is demonstrated that cavily mode can be excited by positioning dipole source in the symmetiy axis of nanoantennas. Switching directions betiveen forward and backward scattering can be achieved by changing parameters of ED emissions.

Nowadays, Longitudinal gravity flow deposits, as a kind of important deep-water reservoirs, can form a certain scale of lithologic oil and gas reservoirs, which is of fundamental significance in the exploration of oil in Saihantala Depression. The evolution and sedimentary characteristics of the longitudinal gravity flow in the east subsag of Saihantala Depression are analyzed based on the core date, well logging, seismic data, regional geological data, and the method of seismic sedimentology. The sedimentary model of the longitudinal gravity flow and the exploration potential of the lithologic reservoir of longitudinal gravity flow are also discussed. The reservoir is mainly composed of medium-fine sandstone with developed secondary pores. The geological conditions for the formation of axial gravity flow are sufficient provenance, the development of slope breaks and the negative axial topography. The updip direction of the longitudinal gravity in the area has a short extension of the sand body, and the downdip direction has thick massive fine sandstones, which opens up pathways for lithologic reservoir exploration.