Initialization speed is one of the most important factors in network real time kinematic(NRTK)performance.Owing to the low correlation among the error sources of reference stations,it is difficult to fix reference sta...Initialization speed is one of the most important factors in network real time kinematic(NRTK)performance.Owing to the low correlation among the error sources of reference stations,it is difficult to fix reference station ambiguities of long-range NRTK quickly.In traditional reference stations ambiguity resolution(AR)methods,baselines are usually solved independently which is called baseline solution(BS)mode in this study.Because the correlations among baselines are not taken into consideration in ambiguities estimation,the AR speed is slow.Generally,tens of minutes or longer time is required to initialize.We propose a network solution(NS)mode approach,in which the correlations among the double-difference ambiguities(DDAs)as well as double-difference ionospheric delays(DDIDs)of different baselines are considered in estimating float ambiguity solutions.Experimental results show that the float ambiguity solutions obtained are more accurate with an improved consistency.Thus,initialization speed is significantly increased by 18%in NS mode.展开更多
The formation of sintering necks between two metal fibers was investigated using the oval-oval model with respect to the fiber angle range of 0°-90°. Surface diffusion was assumed to be the predominant mecha...The formation of sintering necks between two metal fibers was investigated using the oval-oval model with respect to the fiber angle range of 0°-90°. Surface diffusion was assumed to be the predominant mechanism in every section of the junction of two metal fibers in this model, which was addressed numerically using the level- set method. The growth rates of the sintering necks in the direction of the bisector of obtuse angle, the bisector of acute angle and the fiber axis were discussed in detail. It is found that the growth rate of the sintering necks decreases with fiber angle increasing in the direction of the fiber axis and the bisector of acute angle. However, an opposite variation in growth rate of sintering necks can be found in the direction of the bisector of obtuse angle. The numerical simulation results show that the growth rate of the sintering necks is significantly affected by the initial local geomet- rical structure which is determined by the fiber angle.展开更多
Blowing snow is a typical natural hazard in high-altitude and snow-prone regions,and its impact could be significantly reduced by accurate forecasts.The empirical study on the conditions for blowing snow hazards on th...Blowing snow is a typical natural hazard in high-altitude and snow-prone regions,and its impact could be significantly reduced by accurate forecasts.The empirical study on the conditions for blowing snow hazards on the Sichuan-Xizang Highway in high-altitude mountainous areas are conducted in this paper.The study reveals that blowing snow events primarily occur from December to the following February,with the affected roads mainly located in mountainous areas above altitudes of 3000 m.Based on physical characteristics,snow cover is categorized into three types with different processes of snowdrifts:newly fallen or wind-transported snow,slightly consolidated snow,and compacted snow undergoing freeze-thaw cycles,each exhibiting distinct snowdrift formation processes.Field measurement results indicate that the average threshold wind speeds for initiating blowing snow are 9.65,14.77,and 23.15 m s^(-1)at the 10-m height for these three snow types,respectively.Additionally,analyzing the effects of temperature and snowfall timing on threshold wind velocity,a multi-tiered susceptibility model for blowing snow is developed.This model offers enhanced practical applicability for classifying different types of snow and provides more detailed insights into the variations in threshold wind speed during both the early and later stages of snowfall events,compared to models that rely solely on constant thresholds or temperature-based criteria.展开更多
基金supported in part by the National Key Research and Development Program of China(Grant No.2016YFB0800401)in part by the National Natural Science Foundation of China(Grant Nos.61621003,61532020&11472290).
文摘Initialization speed is one of the most important factors in network real time kinematic(NRTK)performance.Owing to the low correlation among the error sources of reference stations,it is difficult to fix reference station ambiguities of long-range NRTK quickly.In traditional reference stations ambiguity resolution(AR)methods,baselines are usually solved independently which is called baseline solution(BS)mode in this study.Because the correlations among baselines are not taken into consideration in ambiguities estimation,the AR speed is slow.Generally,tens of minutes or longer time is required to initialize.We propose a network solution(NS)mode approach,in which the correlations among the double-difference ambiguities(DDAs)as well as double-difference ionospheric delays(DDIDs)of different baselines are considered in estimating float ambiguity solutions.Experimental results show that the float ambiguity solutions obtained are more accurate with an improved consistency.Thus,initialization speed is significantly increased by 18%in NS mode.
基金financially supported by the National Natural Science Foundation of China (Nos. 51174236 and 51134003)the National Basic Research Program of China (No. 2011CB606306)the Opening Project of State Key Laboratory of Porous Metal Materials (No. PMM-SKL-4-2012)
文摘The formation of sintering necks between two metal fibers was investigated using the oval-oval model with respect to the fiber angle range of 0°-90°. Surface diffusion was assumed to be the predominant mechanism in every section of the junction of two metal fibers in this model, which was addressed numerically using the level- set method. The growth rates of the sintering necks in the direction of the bisector of obtuse angle, the bisector of acute angle and the fiber axis were discussed in detail. It is found that the growth rate of the sintering necks decreases with fiber angle increasing in the direction of the fiber axis and the bisector of acute angle. However, an opposite variation in growth rate of sintering necks can be found in the direction of the bisector of obtuse angle. The numerical simulation results show that the growth rate of the sintering necks is significantly affected by the initial local geomet- rical structure which is determined by the fiber angle.
基金Supported by the National Natural Science Foundation of China(52278511)Innovative Development Special Project of China Meteorological Administration(CXFZ2025J071)“Leading the List”Project of Yunnan Meteorological Administration(YNJBGS202306)。
文摘Blowing snow is a typical natural hazard in high-altitude and snow-prone regions,and its impact could be significantly reduced by accurate forecasts.The empirical study on the conditions for blowing snow hazards on the Sichuan-Xizang Highway in high-altitude mountainous areas are conducted in this paper.The study reveals that blowing snow events primarily occur from December to the following February,with the affected roads mainly located in mountainous areas above altitudes of 3000 m.Based on physical characteristics,snow cover is categorized into three types with different processes of snowdrifts:newly fallen or wind-transported snow,slightly consolidated snow,and compacted snow undergoing freeze-thaw cycles,each exhibiting distinct snowdrift formation processes.Field measurement results indicate that the average threshold wind speeds for initiating blowing snow are 9.65,14.77,and 23.15 m s^(-1)at the 10-m height for these three snow types,respectively.Additionally,analyzing the effects of temperature and snowfall timing on threshold wind velocity,a multi-tiered susceptibility model for blowing snow is developed.This model offers enhanced practical applicability for classifying different types of snow and provides more detailed insights into the variations in threshold wind speed during both the early and later stages of snowfall events,compared to models that rely solely on constant thresholds or temperature-based criteria.
