In this paper, by combining measurement-device-independent quantum key distribution (MDI-QKD) scheme with entangled photon sources, we present a modified MDI-QKD scheme with pairs of vector vortex(VV) beams, which shows a structure of hybrid entangled entanglement corresponding to intrasystem entanglement and intersystem entanglement. The former entanglement, which is entangled between polarization and orbit angular momentum within each VV beam, is adopted to overcome the polarization misalignment associated with random rotations in quantum key distribution. The latter entanglement, which is entangled between the two VV beams, is used to perform entangled-based MDI-QKD protocol with pair of VV beams to inherit the merit of long distance. The numerical simulations show that our modified scheme can tolerate 97dB with practical detectors. Furthermore, our modified protocol only needs to insert q-plates in practical experiment.
PM<sub>2.5 </sub>and PM<sub>10</sub> are very important indexes reflecting the air quality in atmospheric environment monitoring. Based on Mie angular scattering theory, a system measuring particulates diameter and concentration of PM<sub>2.5 </sub>and PM<sub>10</sub> was designed, which used optical fiber as transmission medium. Theoretical deduction and Matlab program simulation were presented to illustrate the basic principle of Mie angular scattering. The influences of laser wavelength, detection angle and other parameters on the measurement accuracy were discussed in detail. It had been found that the measurement results had multi-valued problem when the measurement angle range was too small. However, this problem was eliminated obviously when the angle range is greater than 25 degrees.