FY-3D and FY-3C onboard observations for differential code biases estimation     

Li  Xingxing  Ma  Tengzhou  Xie  Weiliang  Zhang  Keke  Huang  Jiaxin  Ren  Xiaodong 《GPS Solutions》2019,23(2):1-16

GPS Solutions - As parameter estimation and statistical testing are often intimately linked in the processing of observational data, the uncertainties involved in both estimation and testing need...  相似文献   

Characteristics of Vegetation Carbon,Nitrogen, and C/N Ratio in a Tamarix chinensis Coastal Wetland of China     

Linping Xie  Baodong Wang  Ming Xin  Min Wang  Xiuping He  Qinsheng Wei  Xiaoyong Shi  Xia Sun 《洁净——土壤、空气、水》2019,47(9)

Variations in carbon (C) and nitrogen (N) of the vegetation in a Tamarix chinensis coastal wetland located in Laizhou Bay, China, are analyzed. It is found that T. chinensis accumulates more C and N than the surrounding herbs, and it allocates more C and N in the aboveground parts but less in the roots. Branches store more C, whereas leaves and flowers accumulate more N than other tissues. The C and N contents in the aboveground parts of T. chinensis are mainly influenced by pH, electrical conductivity (EC), water content, and clay content in the top 100 cm of soil as well as the distance from the sea. For the herbs, their C contents vary little in the supratidal zone, but they are higher than those in the intertidal zone. However, N contents in the herbs are higher in the aboveground parts and varied among different communities. The contents of C and N in the herbs are affected by EC, water content as well as the contents of organic C and total nitrogen (TN) in the top 10 cm of soil. The findings confirm that increasing the biomass of T. chinensis is an effective way to increase C sequestration in temperate coastal wetland.  相似文献   

煤层气赋存的分形特征研究          下载免费PDF全文

王辰  冯增朝  周动  赵东  蔡婷婷 《地球物理学报》2019,62(9):3571-3579

本文利用红外热成像手段，对微小煤样内的甲烷吸附区进行了观察，并评估其吸附特征与在煤中的分布规律.研究表明煤中存在不同尺度与甲烷吸附能力的甲烷富集区，吸附/解吸甲烷时，甲烷富集区比邻近区域具有更明显的升温/降温现象.通过图像处理的方法对不同吸附压力条件下的红外热像图中的甲烷富集区进行提取，采用盒维数进行统计发现甲烷富集区符合分形规律.试验表明随着吸附压力升高，甲烷富集区的分形维数增大，分布初值减小.对两个不同煤田的煤层气富集区进行统计表明：从微米级到千米级尺度范围内，甲烷富集区分布具有分形特征，且分形维数均在1.5~2.00之间.  相似文献   

Aerosol properties over an urban site in central East China derived from ground sun-photometer measurements     

Qi Liu  WeiDong Ding  Lei Xie  JinQiang Zhang  Jun Zhu  XiangAo Xia  DongYang Liu  RenMin Yuan  YunFei Fu 《中国科学:地球科学(英文版)》2017,60(2):297-314

Sun-photometer measurements at Hefei, an urban site located in central East China, were examined to investigate the variations of aerosol loading and optical properties. It is found that aerosol optical thickness (AOT) keeps higher in winter/spring and gets relatively lower in summer/autumn. The large AOT in winter is caused by anthropogenic sulfate/nitrate aerosols, while in spring dust particles elevate the background aerosol loading and the excessive fine-mode particles eventually lead to severe pollution. There is a dramatic decline of AOT during summer, with monthly averaged AOT reaching the maximum in June and soon the minimum in August. Meanwhile, aerosol size decreases consistently and single scattering albedo (SSA) reaches its minimum in July. During summertime large-sized particles play a key role to change the air from clean to mild-pollution situation, while the presence of massive small-sized particles makes the air being even more polluted. These complicated summer patterns are possibly related to the three key processes that are active in the high temperature/humidity environment concentrating on sulfate/nitrate aerosols, i.e., gas-to-particle transformation, hygroscopic growth, and wet scavenging. Regardless of season, the increase of SSA with increasing AOT occurs across the visible and near-infrared bands, suggesting the dominant negative/cooling effect with the elevated aerosol loading. The SSA spectra under varying AOT monotonically decrease with wavelength. The relatively large slope arises in summer, reinforcing the dominance of sulfate/nitrate aerosols that induce severe pollution in summer season around this city.  相似文献   

Effects of different spatial distributions of physical soil crusts on runoff and erosion on the Loess Plateau in China   总被引：1，自引：0，他引：1       下载免费PDF全文

Pei Lu  Xinli Xie  Linhua Wang  Faqi Wu 《地球表面变化过程与地形》2017,42(13):2082-2089

The response of runoff and erosion to soil crusts has been extensively investigated in recent decades. However, there have been few attempts to look at the effects of spatial configuration of different soil crusts on erosion processes. Here we investigated the effects of different spatial distributions of physical soil crusts on runoff and erosion in the semi‐arid Loess Plateau region. Soil boxes (1.5 m long × 0.2 m wide) were set to a slope of 17.6% (10°) and simulated rainfall of 120 mm h^?1 (60 minutes). The runoff generation and erosion rates were determined for three crust area ratios (depositional crust for 20%, 33%, and 50% of the total slope) and five spatial distribution patterns (depositional crust on the lower, lower‐middle, middle, mid‐upper, and upper slope) of soil crusts. The reduction in sediment loss (‘sediment reduction’) was calculated to evaluate the effects of different spatial distributions of soil crusts on erosion. Sediment yield was influenced by the area ratio and spatial position of different soil crusts. The runoff rate reached a steady state after an initial trend of unsteadily increasing with increasing rainfall duration. Sediment yield was controlled by detachment limitation and then transport limitation under rainfall. The shifting time of erosion from a transport to detachment‐limiting regime decreased with increasing area of depositional crust. No significant differences were observed in the total runoff among treatments, while the total sediment yield varied under different spatial distributions. At the same area ratio, total sediment yield was the largest when the depositional crust was on the upper slope, and it was smallest when the crust was deposited on the lower slope. The sediment reduction of structural crust (42.5–66.5%) was greater than that of depositional crust (16.7–34.3%). These results provide a mechanistic understanding of how different spatial distributions of soil crusts affect runoff and sediment production. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

Simulated various characteristic waves in acoustic full waveform relating to cement bond on the secondary interface     

Hongbing Zhang  Danyan Xie  Zuoping Shang  Xuebing Yang  Hongjian Wang  Honggen Tao 《Journal of Applied Geophysics》2011,73(2):139-154

Bad cement bond with water channeling or low strength cement is usually generated on the first and/or secondary interfaces which lie between the cement and casing, and the cement and formation, respectively. It is an inherently complicated problem to evaluate cement bond on the secondary interface (SICB) in a cased borehole. So we need to find a useful wave for evaluating SICB and provide its propagation features. To achieve this, we simulated the acoustic full waveform, 2-D spectrum and dispersion curves in cased boreholes based on the real axis integration method, and a propagator matrix. Simulation results indicated that “casing-cement mode” wave can be utilized to evaluate SICB, as it is most sensitive to water channeling on the secondary interface. Velocity of this mode wave is in between that of the casing wave and the formation wave, so that it is easy to extract it in time. The dispersion curves showed that the casing-cement wave is a dispersion wave, but not a pseudo-Rayleigh wave. Its velocity is obviously larger than v_s of cement. Simulation results further indicated that the amplitude of casing-cement wave is decreasing with increasing cement sheath thickness, but not water channeling thickness, and its travel time is influenced by casing and cement together. Moreover, we investigated factors influencing the casing–cement wave and found that casing diameter and peak frequency are major factors influencing the amplitude and the travel time, while other factors, such as P-wave velocities of cement and wall thickness of casing, are minor factors. But none of these factors greatly influence bond index which is computed from the amplitude. So the bond index has an advantage over the amplitude during evaluating SICB. Formation wave is a helpful signal to evaluate low strength cement without water channeling, and its amplitude is mainly related to the velocities (or impedances) of both cement and formation except for formation attenuation and disturbance wave. Experimental data in calibration pits and field data detecting channeling demonstrated the simulation results.  相似文献   

辽阳灯塔M_S5.1地震震源深度分析     

谢弘臻  王九洋 《中国地震》2018,34(4):704-712

对不同震中距台站的记录采用入射角法、s PL-Pg等震相到时差,对辽宁地震台网记录采用单纯形法研究了辽阳灯塔5.1级地震的震源深度。结果表明,该地震震源深度应为14km,略大于目录给出的10km。利用四川松潘台、青海湟源台的远台记录也得到同样的结果。通过对辽宁1970年以来5.0级以上地震进行分析发现,辽宁地震的震源分布存在东西两侧偏深、中部偏浅、中部地区南浅北深的统计规律,灯塔地震震源深度符合该统计规律。  相似文献   

断层氢气观测技术实验     

谢恒义  李源  夏修军  孙召华 《地震地磁观测与研究》2018,39(4):176-182

采用ATG-6118H痕量氢在线自动分析仪，在朱夏-商丹断裂带南阳地区布设独山、马山口2个氢气观测台，研究设备取气深度、抽气时间设置长短对观测断层氢气浓度的影响，从而为利用痕量氢设备进行断层氢气观测提供参考依据。实验结果表明：①取气深度越浅，观测到的氢气浓度越高，日变化幅度越大；②集气管内氢气浓度偏低时，抽气时间设置略高于导气管路排空时间，氢气浓度明显变化，否则变化不明显。  相似文献   

港湾中海啸流的模拟及其时空演变特征对输入条件不确定性的响应分析          下载免费PDF全文

王培涛  闪迪  侯京明  王岗  高义  任智源  范婷婷  王宗辰  王君成 《地球物理学报》2018,61(4):1325-1340

一直以来，海啸波特征作为表征海啸潜在破坏性的参数指标得到了广泛应用，特别是针对近场极端海啸事件造成的灾害来说，这种表征具有较好的适用性.然而总结分析历史海啸事件造成的损失发现：在远场近岸及港湾系统中，海啸诱导的强流却是造成损失的主要原因.陆架或港湾振荡导致海啸波幅快速升降诱发强流，可能促使港工设施受到威胁及损害，进而对海啸预警服务及海事应急管理提出了新的挑战.因此，全面理解与评估海啸在港湾中诱发的灾害特征，探索港湾中海啸流的数值模拟方法，发展针对港湾尺度的海啸预警服务指导产品尤为迫切.受限于海啸流验证数据的缺乏及准确模拟海啸流技术方法的诸多不确定性，大部分海啸数值模拟研究工作主要是针对水位特征的研究及验证，可能导致对港湾中海啸灾害危险性认识的曲解与低估.本研究基于非线性浅水方程，针对夏威夷群岛三个典型港湾建立了精细化海啸数值模型（空间分辨率达到10 m），并联合有限断层破裂模型计算分析了日本东北地震海啸在三个港湾及其邻近区域的海啸特征，波、流计算结果与实测结果吻合较好，精细化的海啸港湾模型模拟结果可信.模拟发现港湾中较小的波幅，同样可以产生强流.综合分析日本东北地震海啸波、流特征对输入条件不确定性的响应结果发现：港湾中海啸波-流能量的空间分布特征差异较大，这与港湾系统中海啸波的驻波特性相关；相比海啸波幅空间特征，海啸流特征具有更强的空间敏感性；海啸流时空分布特征对输入条件的不确定性响应比海啸波幅对这些不确定性的响应更强，海啸流的模拟与预报更有挑战性；不确定性对海啸流计算精度的影响会进一步传导放大港湾海啸流危险性的评估及对港工设施产生的应力作用的误差，合理的输入条件对海啸流的精确模拟至关重要.最后，希望通过本文的研究可以从海啸波-流特征角度更加全面认识近岸海啸灾害特征，拓展海啸预警服务的广度与深度，从而为灾害应急管理部门提供更加科学合理的辅助决策产品.  相似文献   

Spatiotemporal changes of epidemics and their relationship with human living environments in China over the past 2200 years     

Gong  Shengsheng  Xie  Haichao  Chen  Fahu 《中国科学:地球科学(英文版)》2020,63(8):1223-1226

正Epidemics are biological disasters resulting from the widespread occurrence of acute and severe infectious diseases that are normally caused by viruses, bacteria and parasites.They are amongst the most destructive of all natural disasters suffered by humans (Gong, 2019). The pathogens that cause epidemics have always existed in nature, understanding the spatiotemporal distribution of past epidemics is important for preventing and controlling future epidemics.  相似文献