A dual-band dual-linearly polarized waveguide slot array antenna is proposed in this paper. Two orthogonal slots share a short-circuit wall on broad side. The horizontal and vertical slots, which actualize dual-frequency bands and dual-linear polarization, generate vertically polarized electric fields in 9.39–9.78 GHz and horizontally polarized electric fields in 11.62–12.3 GHz, respectively. The equivalent permittivity of the waveguide is changed by two grooves at the bottom of the waveguide, which improves phase velocity. Two grooves can also reduce the distance between the elements while suppressing the side lobes. Compared to filling the medium in the waveguide, two grooves have less losses. Moreover, the antenna is simple with one input port. The array antenna also overcomes the problems of beam scanning compared with the traditional waveguide slot array antenna. A 1 × 8 antenna array is fabricated and measured to verify the design. The horizontal polarization is formed in 9.39–9.78 GHz, the vertical polarization is generated in 11.62–12.3 GHz, and the antenna gain can reach 15 dBi.

In the past 10–15 years, the government of China has made various efforts in tackling excessive antibiotics use. Yet, little is known about their effects at rural primary care settings. This study aimed to determine the impact of government policies and the COVID-19 pandemic on antibiotic prescribing practices at such settings utilizing data from separate studies carried out pre- and during the pandemic, in 2016 and 2021 in Anhui province, China, using identical sampling and survey approaches. Data on antibiotics prescribed, diagnosis, socio-demographic, etc., were obtained through non-participative observation and a structured exit survey. Data analysis comprised mainly descriptive comparisons of 1153 and 762 patients with respiratory infections recruited in 2016 and 2021, respectively. The overall antibiotics prescription rate decreased from 89.6% in 2016 to 69.1% in 2021, and the proportion of prescriptions for two or more classes of antibiotics was estimated as 35.9% in 2016 and 11.0% in 2021. There was a statistically significant decrease in the number of days from symptom onset to clinic visits between the year groups. In conclusion, measures to constrain excessive prescription of antibiotics have led to some improvements at the rural primary care level, and the COVID-19 pandemic has had varying effects on antibiotic use.

In this paper, the assembly problem of circular-rectangular compound peg and hole parts in automatic assembly is proposed for the first time, and an automatic assembly method based on six-dimensional force sensor is summarized. Firstly, according to the quasi-static equilibrium condition, the contact states are summarized. It is concluded that there are 7 categories of 44 contact states in insertion stage and the forces conditions to maintain each contact state; Secondly, according to the analysis of the force/moment relationship, the jamming diagram is drawn, and the conditions of jamming are analyzed. Thirdly, the assembly strategy is discussed, including contact state recognition strategy, hole searching strategy, and pose adjustment strategy. Finally, combined with impedance control, the assembly theory is verified in ADAMS, and the assembly with minimum clearance of 0.1 mm is achieved.

A mathematical model of variable inclination continuous transverse stub (VICTS) antenna for low sidelobe design is proposed in this paper. VICTS antenna is an antenna with continuous transverse stubs on the parallel-plate waveguide and additional branches attached to the transverse stubs to generate radiation. The antenna using this technique has high aperture efficiency and keeps a significant solution for high-gain antenna. However, the sidelobe level (SLL) of this antenna is relatively high and increases continuously as the pitch angle decreases. This paper presents a fast calculation model for the SLL of VICTS antennas using leaky-wave theory and antenna array theory. The full-wave simulation results and model calculation results are in good agreement, so this model can be used for SLL suppression of VICTS antennas in different frequency bands. By controlling the aperture field distribution to be tapered, the SLL is suppressed to − 23.7 dB using this mathematical model.

Aging treatment plays an important role in strengthening of 2198 Al–Li alloy. Through a serious of heat treatment processes, a large amount of precipitates emerge, mainly observed to be θ′(Al2Cu), Al3Zr, and T1(Al2CuLi), among which, T1 turns to be the most important precipitate that contributes to the strengthening of 2198 Al–Li alloy. While the temperature of the aging process is 175 °C, the density and size of T1 phase keep increasing through the process and reach peak in about 18 h. T1 phase tends to have a certain orientation relationship of ${\left( {0001} \right)_{{{\rm{T}}_1}}}//{\left\{ {111} \right\}_{{\rm{Al}}}}$, ${\left\langle {1010} \right\rangle _{{{\rm{T}}_{\rm{1}}}}}//{\left\langle {110} \right\rangle _{{\rm{Al}}}}$ and may have different kinds of multilayered structures. In most of the multilayered structures, the distance between two adjacent copper-rich laths is less than that in classical single-layered phase. Thus, it can be inferred that the microstructure of T1 phase might change in the process of developing from single-layered structure to multilayered structure. In addition, the interactions between different phases become relatively frequent when the density of T1 phase reaches a threshold.

Due to an increasing number of nuclear reactors in operation, the radiocarbon (14C) released from nuclear power plants (NPPs) has become an important anthropogenic source of 14C. The examination of seasonal Δ14C and monthly Sr/Ca, Mg/Ca variations in a coral in Daya Bay (China) shows that NPPs located there have an impact on the Δ14C level and sea surface temperature (SST). The Mg/Ca variation was in good correlation with the Pacific Decadal Oscillation (PDO) before the operation of Ling’ao NPP in 2002, but this correlation became weak due to an abnormally higher SST after 2002. As illustrated by the Δ14C variation in the coral, there were two relative increases of Δ14C values in 1994 and 2002 when Daya Bay NPP and Ling’ao NPP began operations, respectively. The 14C released from NPPs, instead of oceanic circulation, is probably the primary factor on the Δ14C variation in Daya Bay during the NPPs’ operation. The relative increase in Δ14C value was ~80‰, which equals to ~18 Bq/kgC in specific activity. The seasonal variability in Δ14C value usually peaked in summer, the real reason of which was unknown. This study sheds light on how the NPPs influence the 14C content and SST in surrounding marine environment.

An ancient pottery workshop belonging to the Han Dynasty was excavated in Caoxie village, Hepu County. Caoxie village is an important archaeological site in Hepu County, Beihai City, in south China's Guangxi Zhuang Autonomous Region. It is believed that Hepu County was the oldest departure point on the ancient maritime trading route during the Han Dynasty (206 BC to AD 220) due to the ideal natural geographical conditions and the existence of a large number of Han tombs. Radiocarbon measurements on wood and charcoal samples from the Caoxie village site were performed at the Peking University AMS facility (PKU-AMS), Beijing, and the Centre for Isotopic Research for Cultural and Environmental Heritage (CIRCE) at Naples Second University, Italy. Calibrated ages were obtained with code CALIB 5 (Stuiver and Reimer 1993). The results of these measurements are presented and the related chronology is discussed.

Animal bones and tortoise shells were used for divination by the Chinese royal family during the Shang Dynasty (∼16th–11th century BC), and the divination results were recorded as inscriptions on oracle bones and shells, which are very valuable cultural remains and record many important events in the Shang Dynasty period. Thus, radiocarbon dating of oracle bones was used to build a precise chronology of the late Shang Dynasty. Due to their original burial conditions and the fact that in subsequent decades the pieces were traded or archived in museums, oracle bones are expected to be contaminated with exogenous materials from the environment and the conservation process. During dating, we found that some samples were contaminated by conservation chemical reagents. The contaminated samples were purified by removing exogenous chemicals with a series of organic solvents, in a method modified from Bruhn et al. (2001). Both whole bone and gelatin samples were processed with this purification method, resulting in satisfactory improvements in dating results.

The Fengxi site is near the Feng River in Shaanxi Province, China. Feng City was the capital of the vassal state of Zhou, and the Zhou people lived in this area until the end of the Western Zhou. Serial samples of charcoal, bone, and charred millet were collected from the site and dated by accelerator mass spectrometry (AMS). A sequence model with 6 phases of the Western Zhou dynasty was constructed and the 14C ages were calibrated with OxCal v 3.9. The results showed that the site was used from 1170–1070 BC until 825–755 BC, and the Conquest of Shang by King Wu most probably occurred during 1060–1000 BC.

AMS radiocarbon measurements were started at Peking University in 1992 with a modified HICONEX 834 ion source. Some archaeological samples were measured at a sensitivity of 10−14 with ca. 1.7% precision for modern samples. We have made many improvements in our first two years of operation: a high-intensity Cs sputtering ion source was installed; the graphite sample preparation technique was investigated; and the system stability has been improved. The blank sample background is currently ca. 0.006 MC and a precision within 1% can be reached for modern samples. Geological, archaeological, environmental and biomedical samples can be measured routinely. We present some typical applications.