各向异性介质地震波场的优化褶积微分算子法数值模拟

在前人工作基础上,通过对窗函数参数进行优化实现了对基于Shannon奇异核理论的交错网格褶积微分算子的优化过程.应用这种优化褶积微分算子方法对各向异性介质进行了数值模拟,讨论了优化褶积微分算子法模拟的PML吸收边界条件以及稳定性条件,分析了弹性波在此类介质中的传播特征,并与高阶交错网格有限差分方法进行了对比.数值实验结果表明,该方法适用于各向异性介质中弹性波场模拟,精度高,稳定性好,是一种研究复杂介质中地震波传播的有效数值方法.     

Positional accuracy improvement: a comparative study in Shanghai,China

With the rapid development of geospatial data capture technologies such as the Global Positioning System, more and higher accuracy data are now readily available to upgrade existing spatial datasets having lower accuracy using positional accuracy improvement (PAI) methods. Such methods may not achieve survey-accurate spatial datasets but can contribute to significant improvements in positional accuracy in a cost-effective manner. This article addresses a comparative study on PAI methods with applications to improve the spatial accuracy of the digital cadastral for Shanghai. Four critical issues are investigated: (1) the choice of improvement model in PAI adjustment; five PAI models are presented, namely the translation, scale and translation, similarity, affine, and second-order polynomial models; (2) the choice of estimation method in PAI adjustment; three estimation methods in PAI adjustment are proposed, namely the classical least squares (LS) adjustment, which assumes that only the observation vector contains error, the general least squares (GLS) adjustment, which regards both the ground and map coordinates of control points as observations with errors, and the total least squares (TLS) adjustment, which takes the errors in both the observation vector and the design matrix into account; (3) the impact of the configuration of ground control points (GCPs) on the result of PAI adjustment; 12 scenarios of GCP configurations are tested, including different numbers and distributions of GCPs; and (4) the deformation of geometric shape by the above-mentioned transformation models is presented in terms of area and perimeter.

The empirical experiment results for six test blocks in Shanghai demonstrated the following. (1) The translation model hardly improves the positional accuracy because it accounts only for the shift error within digital datasets. The other four models (i.e., the scale and translation, similarity, affine, and second-order polynomial models) significantly improve the positional accuracy, which is assessed at checkpoints (CKPs) by calculating the difference between the updated coordinates transformed from the map coordinates and the surveyed coordinates. On the basis of the refined Akaike information criterion, the two best optimal transformation models for PAI are determined as the scale and translation and affine transformation models. (2) The weighted sum of square errors obtained using the GLS and TLS methods are much less than those obtained using the classical least squares method. The result indicates that both the GLS and TLS estimation methods can achieve greater reliability and accuracy in PAI adjustment. (3) The configuration of GCPs has a considerable effect on the result of PAI adjustment. Thus, an optimal configuration scheme of GCPs is determined to obtain the highest positional accuracy in the study area. (4) Compared with the deformations of geometric shapes caused by the transformation models, the scale and translation model is found to be the best model for the study area.     

Arctic sea ice thickness variations from CryoSat-2 satellite altimetry data

Arctic sea ice plays an important role in Earth's climate and environmental system. Sea ice thickness is one of the most important sea ice parameters. Accurately obtaining the sea ice thickness and its changes has great significance to Arctic and global change research. Satellite altimeters can be used to derive long-term and large-scale changes in sea ice thickness. The leads detection is vital in sea ice thickness estimation by using satellite altimetry. Different leads detection methods are compared with remote sensing images, and results show that the detection method that uses waveform parameters can obtain improved results. The model for the conversion of freeboard to thickness is optimized by considering the incomplete penetration of snow for radar altimeters. We derive the estimates of the Arctic sea ice thickness for November 2010 to December 2019 by using the CryoSat-2 altimetry data. The sea ice thickness from the IceBridge and draft data from the upward-looking sonar are used to validate our thickness results. Validations show that the accuracy of our thickness estimates is within 0.2 m. Variations in the Arctic sea ice thickness are analyzed using the PIOMAS model and air and sea surface temperatures. A sharp increase in sea ice thickness is found in 2014.     

Lacustrine sedimentological and geochemical records for the last 170 years of climate and environmental changes in southeastern China

Reconstruction of modern climate and environmental changes in east Asia using inland natural climate archives can provide valuable insights on decadal–multidecadal climate and environmental patterns that are probably related to both natural and anthropogenic forcing. Here we investigated an 89‐cm‐long sediment core (TH1) from Tian Lake, southeastern China, for sedimentological, physical and geochemical parameters in order to understand climate and environmental changes for the latest two centuries. ¹³⁷Cs‐ and ²¹⁰Pb‐based age models show that the fine sand–coarse silt‐dominated core contains ~170 years (c. AD 1842–2011) of continuous sedimentation. Sediments with fine sands, low MS values, high water content, high TOC content and a high C:N ratio from c. AD 1842 to 1897 suggest intense hydrological conditions and strong runoff in the catchment, probably because of a humid climate. From AD 1897 to 1990, sediments with very fine sand and coarse silt, high MS values, low water content and unchanged TOC and C:N ratios indicate normal hydrological conditions and in‐lake algae‐derived organic matter. During this interval, the chemical weathering indicators show stronger weathering conditions compared with sediments deposited during AD 1842–1897, supporting the dominance of weathered surface soil input in the earlier interval and physical erosion dominance in the later period, respectively. Since AD 1990, the continuous decrease of geochemical proxies suggests human‐interacted Earth surface processes in the catchment of Tian Lake. A PCA revealed four dominant geochemical controlling factors – detrital input, trophic status, grain size and early diagenesis –, accounting for 26, 20, 18 and 16% of total variance, respectively. This study for the first time provides lacustrine geochemical evidence for the most recent two centuries of climate and environmental changes in coastal southeastern China, a region that is currently undergoing an inversion of critical zone, i.e. an overturning of its soil profile, owing to swift modernization.     

心痛方对急性心肌梗死大鼠CaMKⅡ mRNA表达及钙离子浓度的影响

目的：探究心痛方对心肌梗死大鼠钙调蛋白依赖性蛋白激酶Ⅱ(CaMKⅡ)mRNA表达及钙离子（Ca^{2+）浓度的影响。方法：将50只SD大鼠随机分为5组,分别为假手术组、模型组、心痛方高剂量组、心痛方低剂量组、硫氮卓酮组,采用结扎冠状动脉的方法建立急性心肌梗死大鼠模型,运用RT-PCR法测定各组大鼠心肌组织CaMKⅡ mRNA的表达,激光扫描共聚显微镜法检测心肌组织内Ca2+浓度,HE染色法测定心肌梗死面积。结果：与模型组比较,心痛方高、低剂量组与硫氮卓酮组CaMKⅡ mRNA表达及Ca2+浓度均降低、心肌梗死面积缩小(P<0.01或P<0.05);与心痛方低剂量组比较,心痛方高剂量组、硫氮卓酮组CaMKⅡ mRNA表达、Ca2+浓度均降低(P<0.01),心痛方高剂量组心肌梗死面积缩小(P<0.05);与硫氮卓酮组比较,心痛方高剂量组CaMKⅡ mRNA表达、Ca2+浓度均降低(P<0.01),心痛方高、低剂量组心肌梗死面积均缩小(P<0.01或P<0.05)。结论：心痛方能下调急性心肌梗死大鼠CaMKⅡ mRNA的表达,降低胞内Ca2+浓度,从而拮抗钙超载对心肌细胞的损害,缩小心肌梗死面积。}     

2003-2012年间白令海峡断面淡水构成的时空变化

通过对2003-2012年间白令海峡64.3°N断面海水氧同位素组成的分析,应用海水δ18 O值和盐度的质量平衡关系区分出淡水中河水和海冰融化水组分的贡献,探讨白令海峡淡水组成的分布特征及其年际变化。研究表明,断面东侧阿拉斯加沿岸水影响区呈现低δ18 O值、低盐、高温、高河水组分的特征,西侧阿拉德尔水具有高δ18 O值、高盐、低海冰融化水的特征,中部白令陆架水的δ18 O值、盐度和淡水组成则居于上述二者之间。阿拉斯加沿岸水影响区河水组分的份额约为阿拉德尔水和白令陆架水的2倍,并呈现出2010年2012年2003年2008年的时间变化规律,受控于育空河入海径流量的时间变化。白令陆架水和阿拉斯加沿岸水影响区的海冰融化水份额较为接近,均比阿拉德尔水影响区的海冰融化水份额高约45%。海冰融化水的年际变化表现出2003年2008年≈2012年2010年的规律,受控于白令海海冰的年际变动。从断面淡水构成看,通过白令海峡的淡水平均由46%的河水和54%的海冰融化水构成,且阿拉德尔水、白令陆架水和阿拉斯加沿岸水影响区河水组分与海冰融化水组分的比值自2003年至2012年间呈增加趋势,证明太平洋入流中淡水构成的变化对北冰洋海冰的融化也起着一定的作用。     

滇池污染的成因及其治理新方案

本文对滇池的污染成因进行了综合分析。滇池污染是由两大因素造成的:一是水流太慢,二是污水南侵。从这两大污染因素可以找到两大对策:一是加速湖水流动,二是阻止污水南侵。基于滇池污染实际上是北部污染南部造成的,改变滇池出水口,开挖一条新河道,让滇池水倒流,滇池从原来的下游方换到上游方,城区污水不入滇池,即使进入也能让它快速从北部流出去,北部的污染负荷很容易从北部流出去,南部高水位的水位势压力阻止了北部负荷南侵,解决了滇池污染。     

Space-Time Characteristic Analysis of Wind Field over the South Indian Ocean

1 IntroductionThe South Indian Ocean is the only way which must be passed in marine traffic among Africa, Asia and Oceania. With the development of the international traffic, it becomes more and more frequent to navigate over the South Indian Ocean. More and more hydrometeorological safeguards especially the safeguards of important cruise lines are required. However, data for the region in China is absent except the Indian Ocean Climate Atlas (1973)[1] which has short fixed number of…     

基于多层感知机重建GRACE与GRACE-FO之间数据缺失的黄河流域陆地水储量变化

GRACE重力卫星于2017年6月结束,GRACE-Follow On (GRACE-FO)任务于2018年5月启动,导致了约一年的数据缺失.为了研究长时间序列陆地水储量的变化情况,需要重建这两代重力卫星之间的数据.本文基于多层感知机的神经网络模型,通过将GLDAS、CPC土壤湿度、土壤温度、蒸散量以及降水量等数据作为输入参数,GRACE等效水高作为输出参数来训练神经网络,以黄河流域为研究区域,得到缺失等效水高.通过分析黄河流域等效水高时间序列,得出在2002-2020年间研究区域水储量整体上呈现以-0.51±0.03 cm·a^-1速率减少的趋势.GRACE反演的等效水高相对于降水、蒸散量以及土壤温度滞后时间达2~3个月.通过小波分析验证了GRACE与GLDAS、CPC计算的等效水高具有较强的相关性,且均具有明显的周年共振周期.

     

Aeromagnetic data and geological structure of continental China: A review

We review the latest aeromagnetic geological data of continental China. We discuss the latest achievements in geological mapping and the newly detected features based on aeromagnetic data. Using aeromagnetic data collected for more than 50 years, a series of 1:5000000 and 1:1000000 aeromagnetic maps of continental China were compiled using state-of-the-art digital technology, and data processing and transformation. Guided by plate tectonics and continental dynamics, rock physical properties, and magnetic anomalies, we compiled maps of the depth of the magnetic basement of continental China and the major geotectonic units, and presented newly detected geological structures based on the aeromagnetic data.