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91.
旅行时射线追踪的精度和效率一直是影响地震层析成像质量和效果的关键因素。这里在三维近地表速度结构层析成像应用中,结合旅行时插值算法与最短路径算法,提出了一种三维初至波射线追踪算法。通过对双线性旅行时插值算法进行改进,并运用判定条件与简化插值计算公式进行快速计算,减少了插值次数,降低了运算量,同时也保证了较高的射线精度,有效地解决了三维射线追踪算法的计算低效率,射线精度不高的问题。 相似文献
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以泰国湾 T155号柱状沉积物为研究对象,利用地球化学和矿物学手段探讨了全新世以来泰国湾古气候演化历史。(La/Sm)UCC-(Gd/Yb)UCC指示了全新世以来泰国湾西南部物质来源较为稳定,主要来自于马来半岛,季风控制下的沿岸流是其主要驱动力。通过对高岭石/(绿泥石+伊利石)(ωk/(ωc+ωl))、化学蚀变指数(CIA)和钾铝质量分数比值(ωK/ωAl)的变化规律进行综合研究,将全新世以来泰国湾古气候演化过程划分为两个阶段:①早中全新世(12000~6500calaBP):ωk/(ωc+ωl)值和CIA 值较高,ωK/ωAl值则较低,指示了该段时期强盛的东亚季风;发生于11200~10500calaBP和8500~7500calaBP的冷事件指示了泰国湾对新仙女木事件和8.2ka冷事件的响应;②中全新世(6500calaBP)以来:ωk/(ωc+ωl)值和 CIA 值明显下降,ωK/ωAl值则逐渐上升,指示了该段时间东亚季风呈逐渐减弱的趋势;在3200~1800calaBP时地球化学和黏土矿物指标呈现一个明显低值,对应于热带海域“斜氏普林虫低值事件”,揭示了全球气候变化在泰国湾海域良好的区域性响应特征。 相似文献
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MEI Li TONG Siqin YIN Shan BAO Yuhai HUANG Xiaojun ALATENG Tuya WANG Yongfang GUO Enliang YUAN Zhihui NASHUN Dalai GAO Suriguga LIU Xinyi YE Zhigang 《地理学报(英文版)》2023,33(1):169-194
Water use efficiency (WUE) is an important variable to explore coupled relationships in carbon and water cycles. In this study, we first compared the spatial variations of annual gross primary productivity (GPP) and evapotranspiration (ET) using four GPP and ET products. Second, we selected the products closest to the flux towers data to estimate WUE. Finally, we quantitatively analyzed the impact of climate change and soil water content on WUE. The results showed that: (1) Four GPP and ET products provided good performance, with GOSIF-GPP and FLDAS-ET exhibiting a higher correlation and the smallest errors with the flux tower data. (2) The spatial pattern of WUE is consistent with that of GPP and ET, gradually decreasing from the northeast to the southwest. Higher WUE values appeared in the northeast forest ecosystem, and lower WUE values occurred in the western Gobi Desert, with a value of 0.28 gC m?2 mm?1. The GPP and ET products showed an increasing trend, while WUE showed a decreasing trend (55.15%) from 2001 to 2020. (3) The spatial relationship between WUE and driving factors reveal the variations in WUE of Inner Mongolia are mainly affected by soil moisture between 0 and 10 cm (SM0-10cm), vapor pressure deficit (VPD), and precipitation, respectively. (4) In arid regions, VPD and precipitation exhibit a major influence on WUE. An increase in VPD and precipitation has a negative and positive effect on WUE, with threshold values of approximately 0.36 kPa and 426 mm, respectively. (5) In humid regions, SM0-10cm, VPD, SM10-40cm, and SM40-100cm exert a significant impact on WUE, especially SM0-10cm, and weakens with increasing soil depths, these differences may be related to physiological structure and living characteristics of vegetation types in different climate regimes. Our results emphasize the importance of VPD and soil moisture in regional variability in WUE. 相似文献
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Sedimentary evolution of the Holocene subaqueous clinoform off the southern Shandong Peninsula in the Western South Yellow Sea 总被引:1,自引:0,他引:1
Jiandong Qiu Jian Liu Yoshiki Saito Zigeng Yang Baojing Yue Hong Wang Xianghuai Kong 《中国海洋大学学报(英文版)》2014,13(5):747-760
Based on the stratigraphic sequence formed since the last glaciation and revealed by 3000 km long high-resolution shallow seismic profiles and the core QDZ03 acquired recently off the southern Shandong Peninsula, we addressed the sedimentary characteristics of a Holocene subaqueous clinoform in this paper. Integrated analyses were made on the core QDZ03, including sedimentary facies, sediment grain sizes, clay minerals, geochemistry, micro paleontology, and AMS 14 C dating. The result indicates that there exists a Holocene subaqueous clinoform, whose bottom boundary generally lies at 15–40 m below the present sea level with its depth contours roughly parallel to the coast and getting deeper seawards. The maximum thickness of the clinoform is up to 22.5 m on the coast side, and the thickness contours generally spread in a banded way along the coastline and becomes thinner towards the sea. At the mouths of some bays along the coast, the clinoform stretches in the shape of a fan and its thickness is evidently larger than that of the surrounding sediments. This clinoform came into being in the early Holocene(about 11.2 cal kyr BP) and can be divided into the lower and upper depositional units(DU 2 and DU 1, respectively). The unit DU 2, being usually less than 3 m in thickness and formed under a low sedimentation rate, is located between the bottom boundary and the Holocene maximum flooding surface(MFS), and represents the sediment of a post-glacial transgressive systems tract; whereas the unit DU 1, the main body of the clinoform, sits on the MFS, belonging to the sediment of a highstand systems tract from middle Holocene(about 7–6 cal kyr BP) to the present. The provenance of the clinoform differs from that of the typical sediments of the Yellow River and can be considered as the results of the joint contribution from both the Yellow River and the proximal coastal sediments of the Shandong Peninsula, as evidenced by the sediment geochemistry of the core. As is controlled mainly by coactions of multiple factors such as the Holocene sea-level changes, sediment supplies and coastal dynamic conditions, the development of the clinoform is genetically related with the synchronous clinoform or subaqueous deltas around the northeastern Shandong Peninsula and in the northern South Yellow Sea in the spatial distribution and sediment provenance, as previously reported, with all of them being formed from the initial stage of the Holocene up to the present. 相似文献
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基于Shuttleworth-Wallace Hu(SWH)双源蒸散模型对青藏高原那曲、纳木错、藏东南站蒸散发进行估算,在结果验证良好基础上,对青藏高原蒸散发变化特征及各站主要影响因素进行了分析。结果表明:SWH模型在青藏高原3个草甸站适用性良好;年蒸散发介于388~732 mm之间,年内分布呈先增大后减小特征;3站蒸散发组分差异较大,那曲站和纳木错站土壤蒸发对蒸散总量的贡献分别为53%和56%,藏东南站蒸散发则几乎全部由植被蒸腾贡献,占比高达95%;植被叶面积指数为3站蒸散发最主要的影响因素,饱和水汽压差对藏东南站蒸散发影响也较大。研究结果可对青藏高原蒸散发及其组分时空格局与水循环过程研究提供科学依据。 相似文献
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在大倾角像片的相机检校中,经典共线方程是采用欧拉角(妒,纠,Ⅳ)描述旋转矩阵的,该方法受限于无法获取位置与姿态的初始值,结果可能导致迭代不收敛。共线方程中的旋转矩阵还可以直接利用方向余弦或单位四元数来描述,相机检校时可以无需依赖位置与姿态的初始值。在相同实验数据、初始值和收敛条件的实验中,直接利用方向余弦描述旋转矩阵的方法明显优于单位四元数方法,主要体现在收敛情况和计算结果接近欧拉角方法两个方面。建议在非量测相机检校时,最好选用直接利用方向余弦描述旋转矩阵的共线方程方法。 相似文献
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