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This paper proposes a high-performance receiver for underwater acoustic communications based on time reversal processing for multiple-input multiple-output (MIMO) systems. The receiver employs the vector approximate message passing (VAMP) algorithm as a soft equalizer in turbo equalization. By performing self-iteration between the inner soft slicer and the inner soft equalizer, the VAMP algorithm achieves near-optimal performance. Furthermore, an iterative channel-estimation-based soft successive interference cancellation method is incorporated to suppress co-channel interference in the MIMO system. Additionally, the introduction of passive time reversal technology can combine multiple channels into a single channel, which greatly reduces the computational complexity of the MIMO system, especially for large MIMO systems. The effectiveness of the proposed receiver is verified using experimental data collected in Songhua Lake, China in 2019. The results demonstrate that the proposed receiver significantly reduces the complexity of the traditional parallel-VAMP receiver without sacrificing performance and outperforms other receivers of the same type. Moreover, our experimental results also verify that the VAMP-turbo outperforms the generalized approximate message passing (GAMP)-turbo in terms of bit error rate and convergence performance. [ABSTRACT FROM AUTHOR]

Migratory birds play an important role in the spread of multidrug-resistant (MDR) bacteria. To investigate the prevalence of MDR Escherichia coli in migratory birds in China and potential relationships with the environment, a total of 1387 samples (fecal samples, cloacal swabs, or throat swabs) were collected from migratory birds from three different river basins in China. The collected samples were processed and subjected to bacteriological examinations. Antimicrobial susceptibility testing of the recovered isolates was performed using the E-test for the detection of minimum inhibitory concentrations (MICs). Some antibiotic resistance genes were detected and the PCR products were confirmed by sequencing. In total, 478 (34.7%) E. coli isolates were recovered. The results showed that the drug-resistant E. coli isolates were highly resistant to β-lactams (43.7%) and tetracycline (22.6%), and 73 (15.3%) were MDR, including eight that were extended spectrum β-lactamase-positive. The retrieved strains harbored the blaCTX-M, blaTEM-1, tet(A), tet(B), tet(M), sul1, sul2, sul3, cmlA, floR, and intI1 genes with a prevalence of 5.9%, 36.4%, 80.5%, 11.9%, 6.8%, 6.8%, 47.5%, 12.7%, 50.8%, 37.3%, and 61.0%, respectively. The drug resistance rate of the isolates from southern China was higher than those from northern China. The E. coli samples collected for migratory birds in the Pearl River Basin had the highest proportion (46.7%) MDR isolates. Furthermore, MDR bacteria carried by migratory birds were closely related to the antibiotic content in the basin, which confirms that MDR bacteria carried by migratory birds are likely acquired from the environment. This study also confirmed that migratory birds are potential transmitters of MDR bacteria, demonstrating the need to reduce the use and emission of antibiotics and further in-depth studies on the mechanisms underlying drug resistance of bacteria. [ABSTRACT FROM AUTHOR]

We developed thermal dissociation cavity-enhanced absorption spectroscopy (TD-CEAS) for the in situ measurement of NO 2 , total peroxy nitrates (PNs, RO 2 NO 2), and total alkyl nitrates (ANs, RONO 2) in the atmosphere. PNs and ANs were thermally converted to NO 2 at the corresponding pyrolytic temperatures and detected by CEAS at 435–455 nm. The instrument sampled sequentially from three channels at ambient temperature, 453 and 653 K, with a cycle of 3 min, to measure NO 2 , NO 2+ PNs, and NO 2+ PNs + ANs. The absorptions between the three channels were used to derive the mixing ratios of PNs and ANs by spectral fitting. The detection limit (LOD, 1 σ) for retrieving NO 2 was 97 parts per trillion by volume (pptv) in 6 s. The measurement uncertainty of NO 2 was 9 %, while the uncertainties of PN and AN detection were larger than those of NO 2 due to chemical interferences that occurred in the heated channels, such as the reaction of NO (or NO 2) with the peroxy radicals produced by the thermal dissociation of organic nitrates. Based on laboratory experiments and numerical simulations, we created a lookup table method to correct these interferences in PN and AN channels under various ambient organic nitrates, NO, and NO 2. Finally, we present the first field deployment and compare it with other instruments during a field campaign in China. The advantages and limitations of this instrument are outlined. [ABSTRACT FROM AUTHOR]

China has experienced a sudden multi‐focal and multi‐round of African swine fever (ASF) outbreaks during 2018. The subsequent epidemiological survey resulted in a debate including the possibility of a transboundary spread from European Russia to China through wild boar. We contribute to the debate by assessing a hypothetical overland Euro‐Siberian transmission path and its associated ASF arrival dates. We selected the maximum entropy algorithm for spatial modelling of ASF‐infected wild boar and the Spatial Distribution Modeller in ArcGIS to plot Least Cost Paths (LCPs) between Eastern Europe and NE China. The arrival dates of ASF‐infected wild boar have been predicted by cumulative maximum transmission distances per season and cover with their associated minimum time intervals along the LCPs. Our results show high costs for wild boar to cross Kazakhstan, Xinjiang (NW China) and/or Mongolia to reach NE China. Instead, the Paths lead almost straight eastward along the 59.5° northern latitude through Siberia and would have taken a minimum of 219 or 260 days. Therefore, infected wild boar moving all the way along the LCP could not have been the source of the ASF infection in NE China on 2 August 2018. [ABSTRACT FROM AUTHOR]

In order to solve the problems that the positioning information of the ADS - B transmitter is mainly taken from GPS and the limited distance of the transmission link，the technology of ADS-B monitoring based on"BeiDou"is researched. After a in-depth study on the ADS-B message protocol and making the"BeiDou" communication as a supplementary transmission link to ADS-B，the airborne monitoring terminal system using the"BeiDou"positioning source is designed and the seamless navigation and surveillance technology is studied for aircrafts. RX1E electric general aircraft and the established monitoring center system are used to test and verify the ADS-B and"BeiDou"transmissions of airborne terminal. The results show that the data transmission links realize wide-area surveillance of low-altitude airspace navigable aircraft， and the flight situation information sent by the airborne terminal realize the monitoring center 's online situation awareness of lowaltitude aircraft. The research results provide a technical reference for serving the operational safety of China's general aviation aircraft and improving the informationization level of low altitude airspace management. [ABSTRACT FROM AUTHOR]

This paper presents a CMOS DSRC transmitter architecture for China electronic toll collection systems. A digitally configurable transmitter architecture is proposed to reduce chip area, power, cost, and design complexity. This transmitter consists of only two digitally configurable analog blocks: an ASK modulator and a power amplifier, other than the digital baseband. The use of digital configuration extends output dynamic range, and facilitates rapid prototyping in different process technologies. The RF-SoC is fabricated using a 0.13 μm CMOS technology. Chip measurement results show that the maximum output power from a single-end port is 7.23 dBm, the occupied bandwidth is 2 MHz, the adjacent channel power ratio is −38 dBc at a 10 MHz offset, the adjustment range of modulation index is 77%–95%, and the transmitter dissipates 36 mA in active mode under a 2 V supply. Compared with state-of-the-art designs in the literature, this design demonstrates remarkable advantages in design complexity, modulation index, chip area, power consumption, output dynamic range, and output peak power. The chip area savings is at least 60%, the power consumption is reduced by at least 10%, the output dynamic range is enhanced by 9%, and the single-end output peak power is improved by at least 45%. • This paper presents a CMOS DSRC transmitter architecture for China electronic toll collection systems. • A digitally configurable transmitter architecture is proposed to reduce chip area, power, cost, and design complexity. • The use of digital configuration extends output dynamic range, and facilitates rapid prototyping in different technologies. • The RF-SoC is fabricated using a 0.13 μm CMOS technology. • Chip measurement shows remarkable advantages in chip area, power consumption, output dynamic range, and output peak power. [ABSTRACT FROM AUTHOR]

• A transmitter with bandwidth of 40–100 MHz at 100-kilowatt level was cross-verified through three-dimensional (3D) simulations and experiments. • New phenomenons of high frequency oscillation between the short strip inductor and the shield cavity was found in the input simulation results. • The simulation can provide both the electric field energy and the surface current distribution of the structure of the entire amplifier at a particular power. • The amplifier installed with the new tetrode DB968 achieved the design objectives in the test experiment with 150 and 110 kW power outputs at 48 and 100 MHz, respectively. A 1.5 MW final power amplifier is to be developed for ion cyclotron resonance heating (ICRH) system for the China fusion engineering testing reactor (CFETR) project. First, the feasibility of driver power amplifier with input matching circuit and output resonator cavity and a newly developed tetrode was cross-verified through three-dimensional (3D) simulations and experiments. A single coaxial cavity in parallel with the tetrode covered the frequency range of 40 to 100 MHz at a 100-kilowatt level. In contrast to the previous method of deducing matching parameters using RF circuit and transmission line theory, the use of 3D transmitter simulations provided more accurate matching parameters of tuning components at different operating frequencies. A new phenomenon of high frequency oscillation between the short strip inductor and the shield cavity was found in the input simulation results, which was subsequently verified by experiments. Specific reasons for dividing the output into two parts of high and low frequency were found through output circuit simulations. One is that the length of short stub decreases with the increase of operating frequency, thus decreasing the frequency resolution if all frequencies were using low frequency port. The other is that the coupling capacitor increases sharply with the increase of frequency due to parasitic effect in the low output. Further, the simulation facilitated the study of parasitic effects on matching parameters caused by strip-inductance, inter electrode capacitances of tetrode, and RF cavity. Thus, facilitating the design of final power amplifier in the future. Finally, the amplifier installed with the new tetrode DB968 achieved the design objectives in the test experiment with 150 and 110 kW power outputs at 48 and 100 MHz, respectively. [ABSTRACT FROM AUTHOR]