Hydrological regulation of chemical weathering and dissolved inorganic carbon biogeochemical processes in a monsoonal river     

Jing Liu  Jun Zhong  Hu Ding  Fu-Jun Yue  Cai Li  Sen Xu  Si-Liang Li 《水文研究》2020,34(12):2780-2792

To better understand the mechanisms relating to hydrological regulations of chemical weathering processes and dissolved inorganic carbon (DIC) behaviours, high-frequency sampling campaigns and associated analyses were conducted in the Yu River, South China. Hydrological variability modifies the biogeochemical processes of dissolved solutes, so major ions display different behaviours in response to discharge change. Most ions become diluted with increasing discharge because of the shortened reactive time between rock and water under high-flow conditions. Carbonate weathering is the main source of major ions, which shows strong chemostatic behaviour in response to changes in discharge. Ions from silicate weathering exhibit a significant dilution effect relative to the carbonate-sourced ions. Under high temperatures, the increased soil CO₂ influx from the mineralisation of organic material shifts the negative carbon isotope ratios of DIC (δ¹³C_DIC) during the high-flow season. The δ¹³C_DIC values show a higher sensitivity than DIC contents in response to various hydrological conditions. Results from a modified isotope-mixing model (IsoSource) demonstrate that biological carbon is a dominant source of DIC and plays an important role in temporal carbon dynamics. Furthermore, this study provides insights into chemical weathering processes and carbon dynamics, highlighting the significant influence of hydrological variability to aid understanding of the global carbon cycle.  相似文献   

A hierarchical indexing strategy for optimizing Apache Spark with HDFS to efficiently query big geospatial raster data     

Fei Hu  Yongyao Jiang  Yun Li  Weiwei Song  Daniel Q. Duffy 《International Journal of Digital Earth》2020,13(3):410-428

ABSTRACT

Earth observations and model simulations are generating big multidimensional array-based raster data. However, it is difficult to efficiently query these big raster data due to the inconsistency among the geospatial raster data model, distributed physical data storage model, and the data pipeline in distributed computing frameworks. To efficiently process big geospatial data, this paper proposes a three-layer hierarchical indexing strategy to optimize Apache Spark with Hadoop Distributed File System (HDFS) from the following aspects: (1) improve I/O efficiency by adopting the chunking data structure; (2) keep the workload balance and high data locality by building the global index (k-d tree); (3) enable Spark and HDFS to natively support geospatial raster data formats (e.g., HDF4, NetCDF4, GeoTiff) by building the local index (hash table); (4) index the in-memory data to further improve geospatial data queries; (5) develop a data repartition strategy to tune the query parallelism while keeping high data locality. The above strategies are implemented by developing the customized RDDs, and evaluated by comparing the performance with that of Spark SQL and SciSpark. The proposed indexing strategy can be applied to other distributed frameworks or cloud-based computing systems to natively support big geospatial data query with high efficiency.  相似文献   

星基增强系统L1频段信息服务性能分析     

赵镇  陈刚  胡志刚 《中国地震》2020,36(4):912-923

在北斗全球导航服务进程中，北斗星基增强服务的建设是我国卫星导航事业自身建设和不断完善发展的内在需求，更是我国卫星导航系统标准化建设的必然要求。本文基于星基增强信息定位原理，研究并实现星基增强系统的标准定位算法，采用IGS站点数据及增强信息电文，对WAAS与EGNOS系统服务性能进行分析评估，在“陆态网络”数据处理中，加入SBAS信息也可对相关误差进行改正。结果表明，加入播发的差分改正信息定位精度相对于伪距单点定位显著提高，平面方向统计均方根残差优于1m，高程方向优于1.2m；研究发现受地面参考站分布区域以及电离层、观测星座的影响，WAAS和EGNOS在定位服务性能覆盖范围内均表现出一定的区域性。从总体分析来看，不同系统空间段GEO卫星播发SBAS消息特性不一，均满足单频定位需求，EGNOS稳定性低于WAAS系统，播发消息时有中断现象，在实时单频定位性能方面，WAAS的服务性能较EGNOS得到更优的解算结果。  相似文献   

Season Effects on Subsurface Constructed Wetlands Performance: Role of Radial Oxygen Loss of Phragmites australis     

Qian Wang  Zhenfeng Cao  Yanbiao Hu  Qiang Kong  Fei Xu  Yuanda Du  Congcong Zhao 《洁净——土壤、空气、水》2019,47(8)

  相似文献   

Mechanical behavior of porous solid considering mesoscopic elastic buckling     

Hao-Yue Zhang  Xiao-Xong Hu  Gao-Feng Zhao 《国际地质力学数值与分析法杂志》2020,44(7):962-982

In this work, the elastic buckling of porous solids was investigated using a lattice spring model (LSM). The capability of the LSM to solve elastic buckling problems was comprehensively verified by comparing well-established numerical and analytical solutions. Following this, the buckling of a porous solid was studied, in which two porous structures were considered, ie, the random porous model and the Voronoi porous model. The results reveal that both the porosity and the shape of the pores influence the elastic buckling bearing capacity of the porous solid. Finally, the mechanical responses of a porous solid with an extra high porosity (0.85) were numerically investigated. Our numerical results demonstrated that the nonlinear elastic response of the porous solid might come from its mesoscale elastic buckling. This work shows the ability and promise of using the LSM as a fundamental numerical tool for the deep investigation of the buckling mechanical behavior of porous solids.  相似文献   

Effects of Solid Organic Wastes on Soil Particulate Organic Carbon Structure Under Different Water Conditions     

Xiaojing Qu  Jinggui Wu  Jinghong Zhao  Jianming Li  Juan Hu  Opoku‐Kwanowaa Yaa 《洁净——土壤、空气、水》2019,47(8)

  相似文献   

Analytical solution of seismic response of base-isolated structure with supplemental inerter     

Kun Ye  Shuai Shu  Liang Hu  Hongping Zhu 《地震工程与结构动力学》2019,48(9):1083-1090

Closed-form solutions are derived for the modal characteristics and seismic response of a base-isolated structure equipped with additional inerters. By simplifying the structure-isolator-inerter system in terms of the two-degree-of-freedom (2DOF) model, the modal frequencies, mode shapes, damping ratios, and participation factors of the system are derived. Consequently, analytical seismic response solutions are formulated by the modal superposition method. Utilizing these analytical solutions, an extensive parametric study has been carried out to investigate the effect of supplement inerters on both the modal characteristics and seismic response of the structure-isolator-inerter system. There is a critical inertance leading to the zero second modal participation factor (ie, the disappearance of the second modal response). The associated critical inertance ratio is derived in closed form as well. Moreover, it is observed that the reduction of deformation of isolators by increasing the inertance may be offset by the increase in relative displacements of the superstructure. To circumvent this adverse effect, an optimal range of inertance is identified whereby both the deformation of isolators and the relative displacement of the superstructure are mitigated concurrently.  相似文献   

北部湾典型海岛生态系统服务价值空间异质性对比研究     

田义超  黄远林  张强  陶进  张亚丽  黄鹄  梁铭忠  周国清 《海洋科学》2019,43(2):60-68

基于北部湾海域典型海岛高分1号数据,借助于CART决策树方法,获取了广西北部湾两个典型海岛的景观格局数据,并采用生态系统服务价值计量模型、空间自相关模型及地统计学中的变异函数模型对其生态系统服务价值进行了空间异质性分析。结果表明:团和岛单位面积生态系统服务价值是七星岛的1.08倍,但其变异系数低于七星岛;七星岛由于其地质背景为泥沙岛,景观格局受到人类活动以及自然环境的强烈干扰,趋向于复杂化和破碎化;而团和岛由于所处的外部环境以及自身的地质特征,景观格局呈现出整体斑块化分布状态;团和岛的景观格局主要受到结构性因素的控制,而七星岛则以随机性因素控制为主,选用变程和Moran’s指数来表征其复杂化和破碎化,来决定其优先开发时序,可对前者进行适当开发,而对后者适当进行生态保护;对受到结构性因素影响的岛屿在进行开发时,时序的识别选用变程和Moran’s指数来表征,若变程和Moran’s指数越小,说明海岛整体的景观分布格局趋向于复杂化和破碎化,反之生态系统较好,可进行优先开发。同时本文构建了北部湾海岛生态系统异质性评估与自然资源管理框架,并提出了海岛管理的建议与对策。  相似文献   

建制式反水雷装备发展特点分析及建议     

胡光兰  王久法  李晓东 《数字海洋与水下攻防》2020,3(4):328-332

水雷由于隐蔽性好、威力巨大、效费比高等优点，被许多国家作为重要的一种水种兵器。随着我国海军战略由近海防御向近海防御与中远海护卫转变，反水雷作战范围将延伸到第一岛链以外的海域，针对中远海的反水雷需求，我国应加紧研制建制式反水雷装备，提升编队的反水雷能力。  相似文献   

四川盆地西北部二叠系栖霞阶层序地层特征及地质意义   总被引：2，自引：0，他引：2       下载免费PDF全文

胡笙  谭秀成  罗冰  张本健  张亚  苏成鹏  芦飞凡  李明隆 《古地理学报》2020,22(6):1109-1126

基于露头、钻井岩心和测录井资料,采用层序地层学理论与方法,将四川盆地西北部二叠系梁山组+栖霞组作为一个整体予以解剖,识别出梁山组底界面(Ⅰ型)、栖一段与栖二段界面(Ⅱ型)和栖霞组与茅口组界面(Ⅰ型)3个三级层序界面,将中二叠统栖霞阶划分为2个三级层序: 下部的SQ1层序对应梁山组+栖一段,上部的SQ2层序对应栖二段。通过栖霞阶层序地层格架分析,发现栖霞阶地层存在“底超顶削”的充填规律,统计并绘制SQ1与SQ2层序地层厚度等值线图,对研究区栖霞阶SQ1初期和SQ2期构造—古地理格局进行了恢复,在明确SQ2期为栖霞阶主要成滩期的基础上,结合岩溶发育单元及白云岩展布特征,讨论栖霞阶油气储集意义。结果表明:区内栖霞阶存在北西、北东向隆坳分异,汉南隆起、川北隆起、北缘隆起与广元—旺苍凹陷始终控制了区内沉积格局,指出广元—旺苍海槽雏形始于二叠系栖霞阶。研究区岩溶白云岩孔洞型储集层区与环广元—旺苍凹陷周缘的灰岩岩溶型储集层区为有利的勘探区。  相似文献