Beaver dam analogues drive heterogeneous groundwater–surface water interactions

Beaver dam analogues (BDAs) are a cost-effective stream restoration approach that leverages the recognized environmental benefits of natural beaver dams on channel stability and local hydrology. Although natural beaver dams are known to exert considerable influence on the hydrologic conditions of a stream system by mediating geomorphic processes, nutrient cycling, and groundwater–surface water interactions, the impacts of beaver-derived restoration methods on groundwater–surface water exchange are poorly characterized. To address this deficit, we monitored hyporheic exchange fluxes and streambed porewater biogeochemistry across a sequence of BDAs installed along a central Wyoming stream during the summer of 2019. Streambed fluxes were quantified by heat tracing methods and vertical hydraulic gradients. Biogeochemical activity was evaluated using major ion porewater chemistry and principal component analysis. Vertical fluxes of approximately 1.0 m/day were observed around the BDAs, as was the development of spatially heterogeneous zones of nitrate production, groundwater upwelling, and anaerobic reduction. Strong contrasts in hyporheic zone processes were observed across BDAs of differing sizes. This suggests that structures may function with size-dependent behaviour, only altering groundwater–surface water interactions after a threshold hydraulic step height is exceeded. Patterns of hyporheic exchange and biogeochemical cycling around the studied BDAs resemble those around natural beaver dams, suggesting that BDAs may provide comparable benefits to channel complexity and near-stream function over a 1-year period.     

LabVIEW设计中压力传感器的RBF神经网络温度补偿

在石油平台注水压力监测系统设计中 ,采用LabVIEW虚拟仪器平台 ,嵌入逼近能力强和收敛速度快的RBF神经网络 ,以人工环境实验数据为样本进行训练 ,实现了压力传感器的智能网络温度补偿。结果显示 ,此方法能够在压力、温度变化较大的恶劣环境下 ,获得很高的补偿精度。     

A traveltime reciprocity discrepancy in the Podvin & Lecomte time3d finite difference algorithm

We have found that the extensively used finite difference scheme time3d produces time fields which are 'asymmetric' in the sense that traveltimes computed to the right of the source are faster than traveltimes computed to the left. All finite difference schemes will, as they are approximations to the wave equation, to some extent fail to obey reciprocity perfectly. We show, however, that the errors in time3d may be significant—and unnecessarily large. An asymmetry in the point source initialization has been identified, and after correction time3d produces time fields with an improved reciprocity.     

基于微电子系统（MEMS）加速度地震勘探三分量数字检波器简介

基于微电子机械系统（MEMS）制成的微加速度三分量数字地震检波器。集数据采集、处理及传输功能干一体，在结构模型、工作原理、性能指标控制等方面不同于常规检波器，其信号幅值在低于自然频率范围内没有衰减。因其独特的制造技术，MEMS检波器具有超低噪声，大动态范围和极高的向量保真度性能。     

下庄铀矿田337矿床成矿流体稀土元素示踪

337铀矿床位于下庄矿田东缘,区内发育近EW向、NNE向构造裂隙群及NW向辉绿岩和正长岩脉体,发育以碱性为主的多种围岩蚀变。区内矿床主要赋矿围岩的稀土元素特征属壳源型。矿石内金属矿物以沥青铀矿为主,矿石的LREE/HREE比值为3.25,Sm/Nd比值平均为0.307,Ce/Yb比值为7.127,这些数据都显示出成矿流体具有较深来源。矿石较围岩亏损稀土元素尤其是轻稀土元素,稀土元素分布模式平缓,与幔源辉绿岩特别是与正长岩的稀土元素分布模式相近,负铕异常比围岩更为强烈,反映成矿流体的来源具有幔源性。结合区域地质特征,可以认为337矿床成矿流体来源具有幔源性质。     

DAS24-3B数据采集系统采集控制模块的工作原理

DAS24-3B是中国科学院地质与地球物理研究所研制的宽频带地震数据采集系统。采集控制模块是该系统的重要组成部分。本文阐述了控制模块的工作原理，介绍了DAS24-3B系统的基本组成和采集器工作过程，并给出该系统如何与笔记本端应用程序界面通讯和联络的操作建议，使该系统能够在工作中发挥更大的作用。     

地震前兆仪器嵌入TCP/IP协议的初步试验

根据“十五”总体设计方案的要求，对TCP／IP协议在地震前兆仪器上的实现进行了试验，在有关设备上进行了程序开发，取得了预期的效果。     

用航空POLDER测量仪获取的方向性信息增强对北方森林冠层的识别(英文)

ＰＯＬＤＥＲ（地球反射极化和方向）仪器在ＢＯＲＥＡＳ实验中曾搭载ＮＡＳＡ的一架Ｃ１３０飞机飞行。在ＢＯＲＥＡＳ的南部地区，ＰＯＬＤＥＲ获取了各种实验场地上的ＢＲＤＦ测量值。森林覆盖地区的大的热点特征，以及十个地区上的镜面反射分量得到了描述。该文通过ＰＯＬＤＥＲ的测量数据，对向常规的光谱特征中加入通过遥感获得的方向性特征后，对各种森林覆盖的分类和区分能力的提高给出了定量化的解。当将方向信息加入常规光谱信息后，采用无监督分类时，类间耦合矩阵的各项显著减小（减小倍数为２－５倍）。这一事实证明了用遥感方向特征可以增强对ＢＯＲＥＡＬ森林覆盖的区分能力。