In ground-based GPS meteorology, Tm is a key parameter to calculate the conversion factor that can convert the zenith wet delay（ZWD） to precipitable water vapor（PWV）. It is generally acknowledged that Tm is in an ...In ground-based GPS meteorology, Tm is a key parameter to calculate the conversion factor that can convert the zenith wet delay（ZWD） to precipitable water vapor（PWV）. It is generally acknowledged that Tm is in an approximate linear relationship with surface temperature Ts, and the relationship presents regional variation. This paper employed sliding average method to calculate correlation coefficients and linear regression coefficients between Tm and Ts at every 2°× 2.5° grid point using Ts data from European Centre for Medium-Range Weather Forecasts（ECMWF） and Tm data from ＂GGOS Atmosphere＂, yielding the grid and bilinear interpolation-based Tm Grid model. Tested by Tm and Ts grid data, Constellation Observation System of Meteorology, Ionosphere, and Climate（COSMIC） data and radiosonde data, the Tm Grid model shows a higher accuracy relative to the Bevis Tm-Ts relationship which is widely used nowadays. The Tm Grid model will be of certain practical value in high-precision PWV calculation.展开更多
知识检索增强技术通过引入外部知识库有效缓解了大语言模型(large language models,LLM)的幻觉问题与知识滞后性,成为提升领域任务性能的关键范式。本文针对电网设备缺陷等级识别任务中标注样本缺乏、知识利用率低与可解释性不足的问题...知识检索增强技术通过引入外部知识库有效缓解了大语言模型(large language models,LLM)的幻觉问题与知识滞后性,成为提升领域任务性能的关键范式。本文针对电网设备缺陷等级识别任务中标注样本缺乏、知识利用率低与可解释性不足的问题,提出了一种零样本的知识增强的大语言模型协同推理框架。构建了层次化树状知识库,设计语义最相关的二阶段检索算法提升知识获取效率,并创新性地融合大语言模型先验知识与检索知识进行多阶段推理验证。该方法在218例测试数据上取得54.17%的分类准确率,较无知识检索方法提升了14.26%,同时通过思维链提示生成可验证的解释文本。此外,该方法为零样本,不需要标注数据进行训练。实验结果表明,本方法有效发挥了专业领域知识与通用知识的协同作用,为电力设备缺陷自动检测提供了准确与可解释的解决方案。展开更多
When strong solar activities and geomagnetic storms happen, satellite communications and navigation system will be strongly disturbed. It is of great significance to monitor ionospheric disturbances,because empirical ...When strong solar activities and geomagnetic storms happen, satellite communications and navigation system will be strongly disturbed. It is of great significance to monitor ionospheric disturbances,because empirical models cannot capture ionospheric anomalous disturbances well. Nowadays, dualfrequency GPS(Global Positioning System) observations can be used to estimate the ionospheric total electron content, correct the ionospheric delay and analyze the response of the ionosphere to geomagnetic storms. In this paper, the ionospheric response to the geomagnetic storm occurred in March 2015 is investigated using GPS observations provided by Crustal Movement of Observation Network of China. The result shows that this storm increases the electron density in the ionosphere quickly and disrupts the structure of the northern equatorial anomaly region at the beginning. In the main process stage, compared with that in the quite periods, the VTEC(Vertical Total Electron Content)around the longitude of 120°E decreases by 50% and the amount of depletion is larger in the high latitude region than that in the low latitude region. We also find the height of the peak electron density in F2 layer increases during the geomagnetic storm from the electron density profiles derived from GPS occultation mission.展开更多
The effect of ionospheric delay on the ground-based augmentation system under normal conditions can be mitigated by determining the value of the nominal ionospheric gradient(σvig).The nominal ionospheric gradient is ...The effect of ionospheric delay on the ground-based augmentation system under normal conditions can be mitigated by determining the value of the nominal ionospheric gradient(σvig).The nominal ionospheric gradient is generally obtained from Continuously Operating Reference Stations data by using the spatial single-difference method(mixed-pair,station-pair,or satellite-pair)or the temporal single-difference method(time-step).The time-step method uses only a single receiver,but it still contains ionospheric temporal variations.We introduce a corrected time-step method using a fixed-ionospheric pierce point from the geostationary equatorial orbit satellite and test it through simulations based on the global ionospheric model.We also investigate the effect of satellite paths on the corrected time-step method in the region of the equator,which tends to be in a more north–south direction and to have less coverage for the east–west ionospheric gradient.This study also addresses the limitations of temporal variation correction coverage and recommends using only the correction from self-observations.All processes are developed under simulations because observational data are still difficult to obtain.Our findings demonstrate that the corrected time-step method yieldsσvig values consistent with other approaches.展开更多
基金supported by National Natural Science Foundation of China(41301377)by the Fundamental Research Funds for the Central Universities(2014214020202)by Surveying and Mapping Basic Research Program of National Administration of Surveying,Mapping and Geoinformation(13-02-09)
文摘In ground-based GPS meteorology, Tm is a key parameter to calculate the conversion factor that can convert the zenith wet delay（ZWD） to precipitable water vapor（PWV）. It is generally acknowledged that Tm is in an approximate linear relationship with surface temperature Ts, and the relationship presents regional variation. This paper employed sliding average method to calculate correlation coefficients and linear regression coefficients between Tm and Ts at every 2°× 2.5° grid point using Ts data from European Centre for Medium-Range Weather Forecasts（ECMWF） and Tm data from ＂GGOS Atmosphere＂, yielding the grid and bilinear interpolation-based Tm Grid model. Tested by Tm and Ts grid data, Constellation Observation System of Meteorology, Ionosphere, and Climate（COSMIC） data and radiosonde data, the Tm Grid model shows a higher accuracy relative to the Bevis Tm-Ts relationship which is widely used nowadays. The Tm Grid model will be of certain practical value in high-precision PWV calculation.
文摘知识检索增强技术通过引入外部知识库有效缓解了大语言模型(large language models,LLM)的幻觉问题与知识滞后性,成为提升领域任务性能的关键范式。本文针对电网设备缺陷等级识别任务中标注样本缺乏、知识利用率低与可解释性不足的问题,提出了一种零样本的知识增强的大语言模型协同推理框架。构建了层次化树状知识库,设计语义最相关的二阶段检索算法提升知识获取效率,并创新性地融合大语言模型先验知识与检索知识进行多阶段推理验证。该方法在218例测试数据上取得54.17%的分类准确率,较无知识检索方法提升了14.26%,同时通过思维链提示生成可验证的解释文本。此外,该方法为零样本,不需要标注数据进行训练。实验结果表明,本方法有效发挥了专业领域知识与通用知识的协同作用,为电力设备缺陷自动检测提供了准确与可解释的解决方案。
基金supported by the NSFC (National Natural Science Foundation of China) Project (11573052)
文摘When strong solar activities and geomagnetic storms happen, satellite communications and navigation system will be strongly disturbed. It is of great significance to monitor ionospheric disturbances,because empirical models cannot capture ionospheric anomalous disturbances well. Nowadays, dualfrequency GPS(Global Positioning System) observations can be used to estimate the ionospheric total electron content, correct the ionospheric delay and analyze the response of the ionosphere to geomagnetic storms. In this paper, the ionospheric response to the geomagnetic storm occurred in March 2015 is investigated using GPS observations provided by Crustal Movement of Observation Network of China. The result shows that this storm increases the electron density in the ionosphere quickly and disrupts the structure of the northern equatorial anomaly region at the beginning. In the main process stage, compared with that in the quite periods, the VTEC(Vertical Total Electron Content)around the longitude of 120°E decreases by 50% and the amount of depletion is larger in the high latitude region than that in the low latitude region. We also find the height of the peak electron density in F2 layer increases during the geomagnetic storm from the electron density profiles derived from GPS occultation mission.
基金funding from BRIN through the Research Collaboration Program with ORPA(No.2/III.1/HK/2024)Prayitno Abadi is participating in this study as part of a Memorandum of Understanding for Research Collaboration on Regional Ionospheric Observation at Telkom University(No.092/SAM3/TE-DEK/2021).
文摘The effect of ionospheric delay on the ground-based augmentation system under normal conditions can be mitigated by determining the value of the nominal ionospheric gradient(σvig).The nominal ionospheric gradient is generally obtained from Continuously Operating Reference Stations data by using the spatial single-difference method(mixed-pair,station-pair,or satellite-pair)or the temporal single-difference method(time-step).The time-step method uses only a single receiver,but it still contains ionospheric temporal variations.We introduce a corrected time-step method using a fixed-ionospheric pierce point from the geostationary equatorial orbit satellite and test it through simulations based on the global ionospheric model.We also investigate the effect of satellite paths on the corrected time-step method in the region of the equator,which tends to be in a more north–south direction and to have less coverage for the east–west ionospheric gradient.This study also addresses the limitations of temporal variation correction coverage and recommends using only the correction from self-observations.All processes are developed under simulations because observational data are still difficult to obtain.Our findings demonstrate that the corrected time-step method yieldsσvig values consistent with other approaches.
