An equivalent fractional order orbital angular momentum (OAM) mode based on concentric uniform circular array (CUCA) is proposed in this paper. It is known that the azimuthal resolution of electromagnetic vortex imaging is closely related to the number of OAM modes. Although the multiplein-multiple-out (MIMO) scheme gives better azimuthal resolution than the multiple-in-single-out (MISO) scheme, it suffers aliasing problem, which means the scattering points with their azimuthal difference larger than 180 degree can not be separated correctly. One possible way to solve this is adding fractional modes in MIMO scheme, but unfortunately, fractional modes are unstable and can not transmit to far field. In this paper, an equivalent fractional order OAM mode is introduced to deal with the problem to achieve higher azimuthal resolution by MIMO scheme. The transmitted and received modes are set to be two adjacent integer modes to realize an equivalent fractional mode. Since the radiation patterns generated by uniform circular array (UCA) for different modes are not aligned, concentric uniform circular array (CUCA) is applied and optimized to overcome this shortage. Simulation results demonstrate the validity of the proposed method. INDEX TERMS Orbital angular momentum, radar imaging, fractional mode, concentric uniform circular antenna.

An analysis method based on multi-instruments analysis technique coupled solvent extraction to determine compositions of unknown cosmetic were established. The multi-instruments involve high-performance liquid chromatography (HPLC), X-ray diffraction (XRD) and Fourier transform infrared (FTIR). The cosmetic sample was separated and enriched into 4 fractions by the solvent extraction. The compounds were defined as mercuric ammonium chloride, liquid paraffin, etc.

The vortex electromagnetic (EM) wave carrying orbital angular momentum (OAM) has been introduced in radar imaging to take full advantage of its special phase front. It has been demonstrated that the azimuthal and range resolution are decided by the number of OAM mode and frequency bandwidth respectively. In this paper, theelevation resolution of the vortex wave transmitted by a uniform circular array is derived for the first time through the calculation of correlation function of two closely adjacent points. Since large number of OAM modes should be applied to achieve high-resolution image, which is difficult to realize in practice, the sparse Bayesian learning (SBL) is introduced to reconstruct the targets for 2-D EM vortex imaging. Simulation results show that the targets located at different elevation angle can be reconstructed correctly and higher resolution can be achieved based on the SBL reconstruction algorithm. INDEX TERMS Uniform circular array, orbital angular momentum, radar imaging, sparse Bayesian learning. ZI HE was born in Hebei, China. She received the B.Sc. and Ph.D. degrees in electronic information engineering from the School of Electrical Engineering and Optical Technique, Nanjing

In a conventional electrically conductive adhesive (ECA) preparation process, typical ECAs are made by adding an appropriate amount of electrically conductive fillers, such as silver, into a polymer matrix, such as epoxy resin, to form a uniformly dispersed mixture by mixing and stirring operations. However, during the preparation process, secondary pollution and mass loss are caused by the vigorous mixture process. At the same time, the stirring operation introduces many small and stable bubbles, which affect the electrical conductivity of the ECAs. In light of these problems with the conventional preparation of ECAs, we developed a novel ECA preparation method that employs a powder spraying process: silver flakes are sprayed into the epoxy resin with a certain mass fraction to form formulated pastes. The as-prepared ECAs exhibited excellent properties compared with those prepared by the conventional process. This proves that the powder spraying process is feasible and superior to the conventional process.

A new scheme to achieve high resolution in passive millimeter wave imaging (PMMWI) using electromagnetic (EM) vortex beams is proposed in this article. The spatial resolution of the traditional PMMWI system based on the mechanically or electronically controlled scanning scheme is mainly limited by the beam width of the receiver. However, it is not practical to fabricate an antenna that is too large, another possible way to improve the resolution is to increase the sampling points but will increase the imaging time. In this article, the multimode EM vortex beam is applied to achieve high resolution with less sampling points. The imaging scene is first discretized into small grid cells, and then multimode measurements are conducted during the scanning process to construct equations to solve the unknown brightness distribution. The compress sensing method is applied to reduce the number of orbital angular momentum mode. Simulation results demonstrate that high resolution can be achieved by the proposed method.