No abstract

We propose an interconnected receiver–transmitter surface (IRTS) for simultaneously generating left-hand circularly polarized (CP) beams and right-hand CP beams based on the Pancharatnam–Berry phase, thus realizing dual CP dual beam radiations. The IRTS is composed of upper-layer gradient patches and lower-layer periodic patches that are connected by the metal probes that cross the center tears of the middle metal ground. The lower-layer patches of the IRTS can receive linearly polarized waves and couple the energy into the upper-layer by the metal probe for obtaining dual CP dual beam radiations. In particular, the working bandwidth of the present design can also be further extended when both IRTSs with adjacent working frequency bands are superimposed on each other to form a broadband IRTS (BIRTS). Finally, we fabricate the proposed IRTS and BIRTS with a standard gain horn antenna as the feed and experimentally demonstrate the functionalities of generating dual CP dual beams.

Thermal flowmeters are used more and more widely in liquid flow measurement. In this paper, the mechanical shape of the thermal flowmeter is designed, and the optimal installation position of the thermal probe is determined. In the aspect of measurement mechanism research, three heating methods of the thermal probe are deduced: constant voltage heating method, constant current heating method, and constant power heating method. After reasoning, the constant current heating method is determined to be ideal, so the constant current heating method is selected to heat the speed-measuring probe in the experiment. By analyzing the power factor of convection heat transfer and residual heat source of the heating probe, it is concluded that the measurement range of the thermal flowmeter is 0.5–15 m3/d, the flow in this range is proportional to the electrical signal, and the relative error of measurement is within ±5.8%. According to the analysis of the experimental results, the thermal flowmeter has a simple mechanical structure and no redundant moving parts, which can prolong its service life when used on site. When considering industrial applications, the error may be greater than the laboratory error.

No abstract

In this paper, Yagi antennas are introduced into microwave transmission measuring instruments as the transmit and receive antennas for detecting moisture content in oil-water mixtures. A Yagi antenna is designed, where the simulation results show a peak gain of 9 dBi and the reflection coefficient S11 is lower than ???10 dB in a frequency band of 2.25-4 GHz. Meanwhile, the measurement result using a vector network analyser shows that the Yagi antenna works in the frequency band of 2.9-4.15 GHz, indicating that measurement results shifted to high frequencies. Based on the Yagi antennas, a moisture content measuring system using the microwave transmission method is designed and constructed, where the measurement results show the Yagi directional high-gain microwave antenna used in this paper can achieve water holdup measurement in the range of 0-100%, where the relative error is less than ??15% and the absolute error is within ??2.341%.