Haiqiang Xin

The Tianshan Mountains serve as a critical freshwater reservoir in Central Asia's arid region, playing a key role in regional ecological and economic development. To assess the response of the Tianshan Mountains to climate change, this study analyzes the spatiotemporal dynamics and altitudinal differentiation of land cover using land use transition matrices and annual change rate analysis to assess vegetation shifts under climate variability in the Aksu section of the Tianshan Mountains based on 30-m resolution land cover datasets from 1985, 2005, and 2020 integrated with climate data trends. By focusing on a 35-year period, this research captures significant climate variability and its influence on vegetation and land cover transitions. Notable changes were recorded, with forest areas expanding by 320.5 km² due to increased temperatures and precipitation, grasslands decreasing by 1110.7 km², and snow/ice increasing by 242.8 km² over the study period. Grasslands decreased, with much of this area transitioning to forests and snow/ice. These findings underscore the dual climatic influences of "warming" and "wetting", and the upward shifts in land cover boundaries. These findings distinguish the warming effect that promoted forest expansion from the wetting effect that enhanced snow/ice coverage, underscoring the climatic dual role in shaping high-altitude ecosystems. Innovative applications of land use transition matrices and altitudinal zonation analysis provide a quantitative foundation for understanding climate-induced vegetation shifts. Altitudinal zonation in the Aksu region above 2300 m exhibited a distinct pattern, transitioning from grassland at lower elevations to forest-grassland mosaics, bare land, and finally snow/ice at the highest elevations. These changes highlight the dominant role of climate variability in driving land cover changes over the study period. Furthermore, these findings underscore the ecological implications of grassland loss and forest encroachment. These findings offer critical insights for ecological conservation and sustainable resource management in arid mountain ecosystems.

Low-altitude high-precision 3D traffic maps are crucial navigation tools for UAV and low-altitude aircraft operating in urban airspaces. This paper aims to analyze the current state of technology, key issues, and future development trends of low-altitude high-precision 3D traffic maps. The paper first compares the current status of technological development, application scenarios, policies, regulations, and industrialization. It then delves into future technological trends and critical technological issues that need to be addressed. Finally, it presents a demand analysis and major scientific and technological tasks. Through a comprehensive analysis of technology and market trends, this paper provides guidance for the future development of low-altitude high-precision 3D traffic maps.

The ecological environment is fundamental to human survival and development, and China has seen a historical shift from localized to widespread improvements in its ecological conditions. Aksu, a typical ecologically sensitive region in Xinjiang, China, is significant for the study of vegetation dynamics and their driving factors, which is crucial for ecological conservation. This study evaluates the spatiotemporal changes in vegetation coverage in Aksu from 2000 to 2020 using long-term Normalized Difference Vegetation Index (NDVI) data and trend analysis. Additionally, this study explores key factors influencing vegetation changes through correlation analysis with temperature, precipitation, and nighttime light data. The results indicate the following: (1) vegetation coverage in Aksu exhibits significant spatial heterogeneity, with annual NDVI increasing at a rate of 0.83% per year (p < 0.05); (2) the influence of temperature and precipitation on NDVI was weakly correlated from 2000 to 2020; and (3) a strong positive correlation was found between nighttime light intensity and NDVI, suggesting that urban development plays a dominant role in vegetation change, while temperature and precipitation have comparatively minor impacts. The findings provide a scientific basis for ecological conservation and sustainable development in the region.

The BeiDou Navigation Satellite System (BDS) features a heterogeneous constellation so that it is difficult to mitigate the multipath in the coordinate-domain. Therefore, mitigating the multipath in the observation-domain becomes more important. Sidereal filtering is commonly used for multipath mitigation, which needs to calculate the orbit repeat time of each satellite. However, that poses a computational challenge and damages the integrity at the end of the multipath model. Therefore, this paper proposes a single-difference model based on the multipath hemispherical map (SD-MHM) to mitigate the BDS-2/BDS-3 multipath in a short baseline. The proposed method is converted from double-difference residuals to single-difference residuals, which is not restricted by the pivot satellite transformation. Moreover, it takes the elevation and the azimuth angles of the satellite as the independent variables of the multipath model. The SD-MHM overcomes the unequal observation time of some satellites and does not require specific hardware. The experimental results show that the SD-MHM reduces the root mean square of the positioning errors by 56.4%, 63.9%, and 67.4% in the east, north, and vertical directions; moreover, it contributes to an increase in the baseline accuracy from 1.97 to 0.84 mm. The proposed SD-MHM has significant advantages in multipath mitigation compared with the advanced sidereal filtering method. Besides, the SD-MHM also features an excellent multipath correction capability for observation data with a period of more than seven days. Therefore, the SD-MHM provides a universal strategy for BDS multipath mitigation.

SUMMARY: Human papillomavirus (HPV) has been identified as etiologic agent of various cancers for both men and women. However, HPV vaccine has not been recommended for men in China by far. To provide more evidences to promote HPV vaccination among males at high-risk of infection, this study investigated genital HPV genotypes among male attendees of sexually transmitted disease (STD) clinic. Male attendees (⩾18 years old) were recruited from STD clinic of Beijing Ditan Hospital. Data on sociodemographic characteristics and self-reported sexual behaviors were collected based on questionnaire. Genital swab specimens were collected for HPV genotypes. Finally, a total of 198 eligible participants were included in the study. Nearly half of them were infected with at least one type of HPV. The prevalence of genital infection among participants with only heterosexual behaviors (50·91%, 56/110) was significantly higher than those with only homosexual behaviors (36·36%, 32/88) (P< 0·001). However, the distribution pattern of the most frequently observed HPV subtypes were found to be similar between these two subgroups. HPV31, HPV18, HPV16 and HPV58 were the most frequently identified high-risk types and HPV11, HPV6, HPV81 and HPV61 were the most frequently observed low-risk types. Our results, although need further verification by larger sample size, suggested that currently available HPV vaccines covered most prevalent HPV types observed in Chinese men. As HPV vaccine has been approved for application in females in China, molecular epidemiological studies and intervention studies among high-risk males should be promoted as well.