分类： 地球科学 >> 地理学 提交时间： 2022-05-30 合作期刊: 《干旱区科学》
摘要： Abstract: Hydrothermal condition is mismatched in arid and semi-arid regions, particularly in Central Asia (including Kazakhstan, Kyrgyzstan, Tajikistan, Uzbekistan, and Turkmenistan), resulting many environmental limitations. In this study, we projected hydrothermal condition in Central Asia based on bias-corrected multi-model ensembles (MMEs) from the Coupled Model Intercomparison Project Phase 6 (CMIP6) under four Shared Socioeconomic Pathway and Representative Concentration Pathway (SSP-RCP) scenarios (SSP126 (SSP1-RCP2.6), SSP245 (SSP2-RCP4.5), SSP460 (SSP4-RCP6.0), and SSP585 (SSP5-RCP8.5)) during 20152100. The bias correction and spatial disaggregation, water-thermal product index, and sensitivity analysis were used in this study. The results showed that the hydrothermal condition is mismatched in the central and southern deserts, whereas the region of Pamir Mountains and Tianshan Mountains as well as the northern plains of Kazakhstan showed a matched hydrothermal condition. Compared with the historical period, the matched degree of hydrothermal condition improves during 20462075, but degenerates during 20152044 and 20762100. The change of hydrothermal condition is sensitive to precipitation in the northern regions and the maximum temperatures in the southern regions. The result suggests that the optimal scenario in Central Asia is SSP126 scenario, while SSP585 scenario brings further hydrothermal contradictions. This study provides scientific information for the development and sustainable utilization of hydrothermal resources in arid and semi-arid regions under climate change.
分类： 地球科学 >> 地理学 提交时间： 2022-05-30 合作期刊: 《干旱区科学》
HUANG Xiaoran
BAO Anming
GUO Hao
MENG Fanhao
ZHANG Pengfei
ZHENG Guoxiong
YU Tao
QI Peng
Vincent NZABARINDA
DU Weibing
摘要： Abstract: Glaciers are highly sensitive to climate change and are undergoing significant changes in mid-latitudes. In this study, we analyzed the spatiotemporal changes of typical glaciers and their responses to climate change in the period of 19902015 in 4 different mountainous sub-regions in Xinjiang Uygur Autonomous Region of Northwest China: the Bogda Peak and Karlik Mountain sub-regions in the Tianshan Mountains; the Yinsugaiti Glacier sub-region in the Karakorum Mountains; and the Youyi Peak sub-region in the Altay Mountains. The standardized snow cover index (NDSI) and correlation analysis were used to reveal the glacier area changes in the 4 sub-regions from 1990 to 2015. Glacial areas in the Bogda Peak, Karlik Mountain, Yinsugaiti Glacier, and Youyi Peak sub-regions in the period of 19902015 decreased by 57.7, 369.1, 369.1, and 170.4 km², respectively. Analysis of glacier area center of gravity showed that quadrant changes of glacier areas in the 4 sub-regions moved towards the origin. Glacier area on the south aspect of the Karlik Mountain sub-region was larger than that on the north aspect, while glacier areas on the north aspect of the other 3 sub-regions were larger than those on the south aspect. Increased precipitation in the Karlik Mountain sub-region inhibited the retreat of glaciers to a certain extent. However, glacier area changes in the Bogda Peak and Youyi Peak sub-regions were not sensitive to the increased precipitation. On a seasonal time scale, glacier area changes in the Bogda Peak, Karlik Mountain, Yinsugaiti Glacier, and Youyi Peak sub-regions were mainly caused by accumulated temperature in the wet season; on an annual time scale, the correlation coefficient between glacier area and annual average temperature was 0.72 and passed the significance test at P
分类： 能源科学 >> 能源（综合） 提交时间： 2022-05-30
摘要： Solar stills are considered an effective method to solve the scarcity of drinkable water. However, it is still missing a way to forecast its production. Herein, it is proposed that a convenient forecasting model which just needs to input the conventional weather forecasting data. The model is established by using machine learning methods of random forest and optimized by Bayesian algorithm. The required data to train the model is obtained from daily measurements lasting 9 months. To validate the accuracy model, the determination coefficients of two types of solar stills are calculated as 0.935 and 0.929, respectively, which are much higher than the value of both multiple linear regression (0.767) and the traditional models (0.829 and 0.847). Moreover, by appling the model, it is predicted that the freshwater production of four cities in China. The predicted production is approved to be reliable by a high value of correlation (0.868) between the predicted production and the solar insolation. With the help of the forecasting model, it would greatly promote the global application of solar stills.
分类： 天文学 >> 天文学 提交时间： 2022-05-30 合作期刊: 《天文研究与技术》
摘要： 为提高地平式太阳望远镜库德焦面的指向跟踪精度，文章首先仿真了库德光路中主光轴、方位轴、高度轴、消旋轴不同心时在库德焦面上引入的跟踪误差，分析了库德焦面指向跟踪误差的复杂性，这一问题无法用夜天文望远镜卡焦指向模型解决。然后文章提出了一种基于机器学习的支持向量回归方法来构建太阳望远镜库德焦面的指向跟踪模型，并在NVST望远镜进行了实测建模和实验论证。实验结果表明：在模型改正之前，NVST在库德焦面的指向误差最大值是650.55角秒、RMS是115.88角秒，30分钟跟踪误差是6.46角秒；模型改正之后，指向误差最大值是25.02角秒、RMS值是3.98角秒，30分钟跟踪误差是1.10角秒。由此可见，基于机器学习的支持向量回归建模方法能有效提高地平式太阳望远镜库德焦面的指向跟踪精度。
分类： 天文学 >> 天文学 提交时间： 2022-05-30 合作期刊: 《天文研究与技术》
摘要： 耀斑和日冕物质抛射（Coronal Mass Ejection，CME）期间产生的非热高能粒子流和激波是产生灾害性空间天气事件的两种主要因素，它们主要观测特征分别是具有快速频率漂移特征的射电Ⅲ型暴和具有较为缓慢频率漂移的射电Ⅱ型暴。本文主要介绍了使用概率霍夫变换(Probabilistic Hough Transform)的方法，在观测数据中自动识别出太阳射电Ⅲ型暴和Ⅱ型射电暴，并提取射电Ⅲ和Ⅱ型暴的特征参数，最后利用识别出的射电Ⅱ型暴的物理参数估计了CME激波的速度。
分类： 天文学 >> 天文学 提交时间： 2022-05-30 合作期刊: 《天文研究与技术》
摘要： 相控阵馈源是将阵列天线放置于射电望远镜焦面场处，用以实现更高增益及更灵活波束调控的接收机技术。鉴于其与阵列天线一样，是由多个天线单元以一定方式组合排列而成，工作时阵元之间产生电磁耦合在所难免。本文选用螺旋天线作为阵列天线单元，工作频率为1.25GHz，对独立天线进行仿真优化后，该天线-10dB阻抗带宽仅为70MHz。依托该天线单元建立55矩形排布螺旋天线阵列模型，分别选取阵元间距为1、0.5、0.25、0.125倍波长（1.25GHz@0.24m），以此验证不同阵元间距下的互耦效应对整个阵列带宽的影响。最终通过对各阵元输入阻抗进行匹配，仿真得到在0.25倍波长间距下，阵列中心阵子的-10dB阻抗带宽可扩展至550MHz，而阵列天线的带宽也基本表征了将其用作相控阵馈源的工作带宽。上述工作加深了对阵列天线带宽特性的理解，也为实际应用于射电望远镜系统的相控阵馈源实现更宽的工作带宽提供了可能。
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