Interaction of multiple courses of wave‐induced fluid flow in layered porous media

Different theoretical and laboratory studies on the propagation of elastic waves in layered hydrocarbon reservoir have shown characteristic velocity dispersion and attenuation of seismic waves. The wave‐induced fluid flow between mesoscopic‐scale heterogeneities (larger than the pore size but smaller than the predominant wavelengths) is the most important cause of attenuation for frequencies below 1 kHz. Most studies on mesoscopic wave‐induced fluid flow in the seismic frequency band are based on the representative elementary volume, which does not consider interaction of fluid flow due to the symmetrical structure of representative elementary volume. However, in strongly heterogeneous media with unsymmetrical structures, different courses of wave‐induced fluid flow may lead to the interaction of the fluid flux in the seismic band; this has not yet been explored. This paper analyses the interaction of different courses of wave‐induced fluid flow in layered porous media. We apply a one‐dimensional finite‐element numerical creep test based on Biot's theory of consolidation to obtain the fluid flux in the frequency domain. The characteristic frequency of the fluid flux and the strain rate tensor are introduced to characterise the interaction of different courses of fluid flux. We also compare the behaviours of characteristic frequencies and the strain rate tensor on two scales: the local scale and the global scale. It is shown that, at the local scale, the interaction between different courses of fluid flux is a dynamic process, and the weak fluid flux and corresponding characteristic frequencies contain detailed information about the interaction of the fluid flux. At the global scale, the averaged strain rate tensor can facilitate the identification of the interaction degree of the fluid flux for the porous medium with a random distribution of mesoscopic heterogeneities, and the characteristic frequency of the fluid flux is potentially related to that of the peak attenuation. The results are helpful for the prediction of the distribution of oil–gas patches based on the statistical properties of phase velocities and attenuation in layered porous media with random disorder.     

对东日本大地震序列潜热通量异常现象的讨论

用美国国家环境预报中心的表面潜热通量数据,对2011年东日本大地震序列前后所出现的潜热通量异常展开讨论,结合主震震中周边区域在1991~2011年的中强地震序列数据,分析了潜热通量异常与地震之间的关系。结果表明:(1)东日本大地震前的潜热通量剧烈变化不一定是异常,且不一定由此次地震活动引起;(2)该研究区域内20年间出现过多次有疑似"热异常"却无明显震例与之相对应的情况;(3)该研究区域内20年间有超过60%的中强地震震前并无"热异常"出现;(4)在研究潜热通量变化是否属于异常时,应尽量多地考虑各个方面的影响因素,科学合理地设定判断参数;(5)在研究潜热通量异常与地震的关系时,应对特定区域作长时间序列分析,而不是单纯针对短期内的个别震例进行判别。     

鄱阳湖入湖、出湖污染物通量时空变化及影响因素(2008-2012年)

研究鄱阳湖入、出湖污染物通量是加强鄱阳湖及长江水功能区限制纳污红线管理的前提,是建立鄱阳湖水质预测模型的基础.基于2008-2012年鄱阳湖8条主要入湖河流、出湖口的逐月水量、水质同步监测资料,根据污染源特征优选算法,计算总磷(TP)、氨氮(NH3-N)、高锰酸盐指数(CODMn)的入、出湖污染物通量,并分析时空变化特征及影响因素.结果表明:(1)出湖口和乐安河入湖口断面的NH3-N、TP及昌江入湖口断面的TP,以点源污染为主,采用每月瞬时通量作为月平均通量的算法更准确;其余以非点源污染为主,采用瞬时污染物浓度与月平均流量之积来计算月平均通量更准确.(2)2008-2012年CODMn、NH3-N和TP年平均人湖通量分别为304398、53063和9175 t,年平均出湖通量分别为367436、45814和8452t.8条入湖河流每年的入湖水量、CODMn通量和个别年份的NH3-N、TP通量小于出湖,这主要是因为未计算区间产流及相应排污和采砂引起的内源污染.(3)入、出湖污染物通量在年际间主要受水量影响而呈现W型波动变化趋势,CODMn、NH3-N、TP入湖通量及CODMn出湖通量均集中在汛期,NH3-N、TP出湖通量则是冬季较多(低水位下湿地植被净化作用受限).入湖TP、NH3-N、CODMn通量主要来自赣江、信江、乐安河,而NH3-N、TP浓度最高的是乐安河、信江.     

Comparison of three remote sensing based models for the estimation of latent heat flux over India

The aim of this work is to compare three remote sensing based models: two contextual and one physically-based single-pixel model for the estimation of daytime integrated latent heat flux without the use of any ground measurements over Indian ecosystems. Satellite datasets from the MODIS sensors aboard the Terra and the Aqua satellites were used. The latent heat flux estimated from the remote sensing models was compared with that estimated from Bowen ratio energy balance towers at five sites in India. The root mean square error (RMSE) of the latent heat flux estimated from the contextual and the physically-based models was found to be in the order of 40 and 70 W m^?2, respectively. The relatively inferior performance of the more complex physically-based model in comparison with the contextual models was found to be largely due to inaccurate parameterizations estimated only from remote sensing datasets without any ground data.     

Video-monitoring of wood discharge: first inter-basin comparison and recommendations to install video cameras

Wood in rivers plays a major role both ecologically and morphologically. In recent decades, due to human activities in the river channels and along the riparian zone, wood obstruction and jamming has exacerbated flooding hazards and infrastructure damage. Therefore, it is necessary to quantify the wood flux and discharge in rivers to improve wood hazard management. Among the various methods for monitoring the wood flux in a river, the streamside videography technique is effective given its high temporal and spatial resolution. Previous work monitored the wood discharge (m³/s) using this technique in the Ain River (France) during three floods (MacVicar and Piégay, 2012), and the same method is implemented on the Isère River (France) to obtain the statistics of wood discharge for two floods. Comparison between the two sites supports the generalization of both the monitoring technique and the link between wood discharge and flood characteristics. We first show that the maximum wood discharge is observed at bankfull discharge, and we confirm the three stage model proposed by MacVicar and Piégay (2012). Additionally, transverse distributions of the number of wood pieces and corresponding wood length appear to be similar for different flood magnitudes on each site. As a technical contribution, the use of the same technique on two sites allows for recommendations on key decisions related to the location and implementation of the equipment. Both statistical and technical contributions can be used by decision makers to implement this monitoring technique, acquire the wood transport parameters, and evaluate the potential wood hazards at local scale or along a river. © 2020 John Wiley & Sons, Ltd.     

模拟强震后高压输电接续管漏磁的检测方法研究

为维持强震影响下电力系统安全运行,改善高压输电效率及输电质量,提出强震影响下高压输电接续管漏磁检测方法。采用磁敏传感器获取漏磁通内的漏磁信号,通过计算提取接续管内漏磁信号特征量,依据这些特征实现高压输电接续管漏磁检测。构建高压输电接续管三维有限元几何模型,通过对模型的单元类型确定、材料选择、边界条件与荷载设置、传感器部署位置等,完成高压输电接续管仿真分析。实验结果表明：在Ⅸ度罕遇北京波影响下,接续管内漏磁信号特征量可评判缺陷深度,实现接线管漏磁检测。通过对DL/T1192-2012标准输电线接续管上表面和下表面两端的漏磁信号峰值检测等,证明了本文方法对强震影响下高压输电接续管漏磁进行检测的有效性。     

The magnetic field strength and energy flux of energetic electrons in a microwave burst source region

The observations of a microwave burst with multiple impulses on 1993 Oct 2, 073940–074100 UT are analysed. This event consists of multiple impulses superimposed on a slowly varying burst background. Our formula for coronal magnetic field diagnostics was used here for the first time to derive the field strength and information on the energetic electrons. The results are: 1) The mean spectral index of the impulsive component in the optically thin part is less than that of the slow background by 1 (a harder spectrum). The mean brightness temperature at 19.6 GHz of the former is 6 times that of the latter. 2) The mean magnetic strengths of the impulse and slow burst regions are 158 G and 531 G, respectively. The time variation in the slow burst region is saddle-shaped, being 50% lower in the middle than at the beginning and end. 3) The column density NL and number density N of energetic electrons in the impulsive component are 4% and 8% of those of the slow component, but the energy flux and emission coefficient are 100% and 800% greater. The two components appear to be produced by two different electron groups with different energy distributions in two different regions.     

西北内陆河流域“自然—社会—贸易”三元水循环模式解析

持续的强人类活动大大改变了流域水循环演变的结构、路径和驱动力,后者又反过来影响着人类生存发展的水安全。日益深入的市场经济使人类活动对水循环的影响从一个流域扩展到流域之外更宽广的区域范围,以产品贸易为纽带的水“流动”已成为驱动区域水循环演变与影响区域水安全的重要内在因素。以流域为单元的传统水循环研究,难以揭示不同区域之间的水循环联系、双向回馈机制与协同进化机理。本文从西北内陆河流域长期大量输出高耗水农产品这一现象分析入手,采用理论解析与案例相结合方法,阐述分析内陆河流域自然水循环、“自然—社会”二元水循环、区域间贸易水循环的基本过程、显著特征及其驱动机制,继而首次明确提出内陆河流域“自然—社会—贸易”三元水循环模式,并就其通量计量模型、影响因素与生态环境效应、科学前沿进行了探索分析,以便未来西北内陆河水循环、水文水资源等研究能更多重视对驱动内陆河流域水循环的外部力量及其双向互馈、协同进化的分析,更新内陆河流域水安全、生态安全的思考范式。     

Distribution of Dissolved Inorganic Carbon （DIC） and Its Related Parameters in Seawater of the North Yellow Sea and off the Qingdao Coast in October, 2007

Data on the distribution of dissolved inorganic carbon (DIC) were obtained from two cruises in the North Yellow Sea (NYS) and off the Qingdao Coast (QC) in October, 2007. Carbonate parameters were calculated. The concentrations of DIC are from 1.896–2.229 mmolL⁻¹ in the NYS and from 1.939–2.032 mmolL⁻¹ off the QC. In the southwest of the NYS, DIC in the upper layers decreases from the north of the SP (Shandong Peninsula) shelf to the center of the NYS; whereas in the lower layers DIC increases from the north of the SP shelf to the center of the NYS and South Yellow Sea. In the northeast of the NYS, DIC in all layers increases from the YR (Yalu River) estuary to the centre of the NYS. The distribution of DIC in NYS can be used as an indicator of Yellow Sea Cold Water Mass (YSCWM). Air-sea CO₂ fluxes were calculated using three models and the results suggest that both the NYS and the QC waters are potential sources of atmospheric CO₂ in October.     

Analysis and prediction of influence imposed on Jiaozhou Bay tidal currents and tidal energy of M2 tidal system by Jiaozhou Bay reclamation

The 3-D ECOMSED ocean model was applied to establish a time-dependent boundary model for Jiaozhou Bay (JZB), in which the operator-splitting technique was used and the ‘dry and wet’ method was introduced. The influence caused by JZB reclamation on the surface level, residual currents, tidal system and tidal energy of M₂ tidal system were predicted and analyzed. The results show that JZB reclamation has slight impact on the M₂ tidal system, in which the variation of amplitude and phase is less than 1%.The changes of the currents and residual currents in Qian Bay and near the reclamation areas are greater, but in other areas the changes are smaller, in which the currents have a change of around 1%, while the residual currents change ranges from 1.82%–9.61%. After reclamation, the tidal energy fluxes increase by 2.62%–5.24% inside and outside the JZB mouth, but decrease by 20.21%–87.23% near Qian Bay and the reclamation area.