K-/Ka-Band Dual-Polarized Differential Series-Fed Waveguide Slot Array Antenna with Enhanced Boresight Radiation Bandwidth

This communication presents a hollow-waveguide (HW) differential series-fed continuous transverse stub (CTS) based dual-band dual-polarized antenna (DBDPA) with wideband boresight radiation characteristics. The realization of the dual-band dual-polarized performance is based on the orthogonal layout of series-fed dual-band CTS elements. To ensure the boresight radiation of both polarizations at the center frequencies of two target bands, a 2-D slow-wave structure (SWS) is loaded in the parallel-plate waveguide (PPW) to flexibly modulate the guided wavelengths to match the physical periods of CTS elements. By further employing two sets of orthogonal differential feeding networks, the frequency-induced squint beams can be superposed to form a boresight main beam in a wideband. Combined with the optimization of the physical period, the boresight radiation bandwidth with stable patterns in both bands has been improved. A prototype is fabricated and demonstrated. The measured results indicate that the boresight radiation bandwidth for both polarizations is extended to 17.5-20 GHz (K-band) and 28.5-30 GHz (Ka-band), respectively. In these two frequency ranges, the antenna efficiencies are both larger than 85%.</p

Evaluation of Uncertainty in Determination of Sucralose in Soy Sauce by High Performance Liquid Chromatography

Objective: To establish an evaluation method for the uncertainty of high-performance liquid chromatography in the determination of sucralose in soy sauce. Methods: Testing was conducted in accordance with the national food safety standard GB 22255-2014. The content of sucralose in soy sauce was analyzed in accordance with the national metrological technical specification JJF 1059.1-2012. An uncertainty evaluation mathematical model was established to analyze the uncertainty factors during the measurement process. The uncertainty of the test results was evaluated and calculated through repeated sample measurements, standard solution purity, standard curve, glassware, weighing process, recovery rate, and testing instruments. Results: According to the confidence interval of 95%, the content of sucralose in soy sauce was (0.048±0.007) g/kg, k=2. Conclusion: The evaluation method for the uncertainty of sucralose in soy sauce by high performance liquid chromatography was established. The sources of the uncertainty of the determination results of sucralose in soy sauce were finally determined as follows: The fitting of the standard curve established by sucralose standard solution, and the recovery rate. And the proportion of various uncertainty evaluation factors in the process of determining sucralose content in soy sauce was cleared

Silver-modified polyniobotungstate for the visible light-induced simultaneous cleavage of C–C and C–N bonds

Silver-modified polyniobotungstate based on Nb/W mixed-addendum polyoxometalate with formula Ag9[P2W15Nb3O62]·21H2O (Ag-Nb/W) was synthesized and then characterized by various analytical and spectral techniques. Ag-Nb/W was proven to be an efficient photocatalyst for the oxidative ring opening of 2-phenylimidazo[1,2-a]pyridine via the simultaneous cleavage of C–C and C–N bonds. Under visible light (430–440 nm) and with oxygen as an oxidant at room temperature, Ag-Nb/W can catalyze the rapid transformation of various 2-phenylimidazo[1,2-a]pyridine derivatives to produce the corresponding oxidative ring-opening product N-(pyridin-2-yl) amides in good isolated yields ranging from 65% to 78%. As a heterogeneous photocatalyst, Ag-Nb/W showed excellent sustainability and recyclability in the recycling experiments. Infrared (IR) spectroscopy and X-ray diffraction (XRD) analysis indicated that Ag-Nb/W could retain its integrity after catalysis. A possible mechanism involving the singlet oxygen for the catalytic reaction was proposed

Feasibility of Solar Updraft Towers as Photocatalytic Reactors for Removal of Atmospheric Methane–The Role of Catalysts and Rate Limiting Steps

Due to the alarming speed of global warming, greenhouse gas removal from atmosphere will be absolutely necessary in the coming decades. Methane is the second most harmful greenhouse gas in the atmosphere. There is an emerging technology proposed to incorporating photocatalysis with solar updraft Towers (SUT) to remove methane from the air at a planetary scale. In this study, we present a deep analysis by calculating the potential of methane removal in relation to the dimensions and configuration of SUT using different photocatalysts. The analysis shows that the methane removal rate increases with the SUT dimensions and can be enhanced by changing the configuration design. More importantly, the low methane removal rate on conventional TiO2 photocatalyst can be significantly improved to, for example, 42.5% on a more effective Ag-doped ZnO photocatalyst in a 200 MW SUT while the photocatalytic reaction is the rate limiting step. The factors that may further affect the removal of methane, such as more efficient photocatalysts, night operation and reaction zone are discussed as possible solutions to further improve the system