绝对重力仪激光器光纤对准调节方法概述     

任敏拴  商永杰  郑文科  康胜军  赵丕 《大地测量与地球动力学》2020,40(9):981-984

绝对重力仪激光器光纤由于应力变化、形状改变、震动或耦合器维护等原因破坏了输出激光的偏振态,使其在光纤内的传输变得非常不稳定,导致光纤输出激光的消光比值小于100,无法满足绝对重力观测条件。针对该问题,介绍了光纤对准调节的方法,通过设计消光比检测装置检验消光比值是否大于100。对#181和#250两台WEO100型He-Ne激光器的光纤进行对准调节实验,并通过消光比检测装置实测,两台激光器输出的光束消光比值满足绝对重力测量的条件,表明该对准调节方法科学有效。  相似文献   

正循环机械回转钻孔灌注桩在卵石层中的应用     

皮跃进 《福建地质》2009,28(3):250-252

在粒径、密实度较大的卵石层采用正循环机械回转钻进行灌注桩施工,存在钻具类型、合理的泥浆比例和钻探工艺等问题。以西安绕城高速公路谢王立交桥桥桩基工程实践为例,探讨正循环机械回转钻孔灌注桩在卵石层施工工艺等问题。  相似文献   

Formation of iron plaque on mangrove roots receiving wastewater and its role in immobilization of wastewater-borne pollutants   总被引：2，自引：0，他引：2  

Pi N  Tam NF  Wong MH 《Marine pollution bulletin》2011,63(5-12):402-411

Iron (Fe) plaque formed on mangrove root increased with wastewater discharge, but the extent was species-specific. For Bruguiera gymnorrhiza, Fe plaque concentration was 0.80 mg g(-1) root d.wt at Day 0 and increased to 4.59, 6.84 and 7.52 mg g(-1) at Day 75 in the fresh water control (FW), synthetic wastewater with pollutant concentrations five times of municipal sewage (5SW) and double of 5SW (10SW) treatments, respectively; the respective increases in Excoecaria agallocha were from 0.70 to 2.37, 10.73 and 13.21 mg g(-1). For Acanthus ilicifolius, similar increase was found in 5SW, but all of the plants were dead in 10SW at Day 75. The concentrations of heavy metals and phosphorus immobilized were positively correlated with the amounts of Fe plaque formed, but the regression coefficients varied among species. The performance of mangrove plants in wastewater treatments was related to the Fe plaque formed and its immobilized wastewater-borne pollutants.  相似文献   

Comparative phylogeography of African rain forest trees: A review of genetic signatures of vegetation history in the Guineo-Congolian region     

Olivier J. Hardy  Céline Born  Katarina Budde  Kasso Daïnou  Gilles Dauby  Jérôme Duminil  Eben-Ezer B.K. Ewédjé  Céline Gomez  Myriam Heuertz  Guillaume K. Koffi  Andrew J. Lowe  Claire Micheneau  Dyana Ndiade-Bourobou  Rosalía Piñeiro  Valérie Poncet 《Comptes Rendus Geoscience》2013,345(7-8):284-296

The biogeographic history of the African rain forests has been contentious. Phylogeography, the study of the geographic distribution of genetic lineages within species, can highlight the signatures of historical events affecting the demography and distribution of species (i.e. population fragmentation or size changes, range expansion/contraction) and, thereby, the ecosystems they belong to. The accumulation of recent data for African rain forests now enables a first biogeographic synthesis for the region. In this review, we explain which phylogeographic patterns are expected under different scenarios of past demographic change, and we give an overview of the patterns detected in African rain forest trees to discuss whether they support alternative hypotheses regarding the history of the African rain forest cover. The major genetic discontinuities in the region support the role of refugia during climatic oscillations, though not necessarily following the classically proposed scenarios. We identify in particular a genetic split between the North and the South of the Lower Guinean region. Finally we provide some perspectives for future study.  相似文献   

Assessment of a new solution for tracking pebbles in rivers based on active RFID          下载免费PDF全文

Mathieu Cassel  Thomas Dépret  Hervé Piégay 《地球表面变化过程与地形》2017,42(13):1938-1951

Low‐frequency passive integrated transponders (PIT tags), are commonly used for monitoring pebble mobility in gravel‐bed rivers. Although early studies reported high recovery rates for PIT tags used in small streams, recovery rates in larger systems remain low, substantially limiting the possibilities for their use in such rivers. These low recovery rates are potentially due to missed detections caused by tag signal collision, burial in the sediment layer deeper than the maximum detection range and insufficient (but still exhausting) field effort to cover the concerned areas. A potential solution for addressing these problems is to use active ultra‐high frequency (a‐UHF) transponders as these have a greater detection range and anti‐collision protocols. In order to assess the potential of such transponders for pebble tracking in rivers, we used 433.92 MHz COIN‐ID and COIN‐HC models (ELA Innovation Company, Montpellier, France). We completed several tests to (i) characterize transponder detection ranges in the water and in saturated sediment and (ii) develop field protocols for locating tags by combining global positioning systems (GPS) sites and transponder received signal strength indication (RSSI) levels. The results showed that (i) the maximum detection ranges are about 2.4 m in the water column and more than 2.6 m in a column of saturated gravelly‐sandy sediment, (ii) RSSI spatial interpolation can be used to determine transponder position with good accuracy (< 1 m), (iii) the desired minimal level of accuracy can be adjusted depending on in‐field effort and signal impulse interval, (iv) the RSSI maximal value observed cannot yet be used to determine transponder burial depth because of the multipath propagation of radio frequencies and the semi‐directional emission of the tag signal. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

Multidimensional Toxicity of Rhamnolipid Extracts Obtained From Creosote‐Contaminated Soil          下载免费PDF全文

Zuzanna Sydow  Piotr Lisiecki  Justyna Staninska‐Pięta  Anna Olejnik  Paweł Cyplik  Agnieszka Zgoła‐Grześkowiak  Roman Marecik  Jacek Nowak  Katarzyna Glazar  Agnieszka Piotrowska‐Cyplik 《洁净——土壤、空气、水》2018,46(5)

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基于RS和GIS的临武县矿山地质环境调查评价          下载免费PDF全文

刘博  姚腾飞  皮建高  周鑫  王璨 《中国地质灾害与防治学报》2020,31(1):135-142

本文通过遥感解译和实地核查,查明了临武县主要的矿山地质环境问题,并对矿山地质环境问题和地质环境背景条件进行分析研究,建立矿山地质环境综合评价指标体系,应用"专家打分-层次分析法"确定评价指标权重,根据相关规范确定评价指标等级,建立评价模型。基于ArcGIS平台,对各指标进行信息提取、赋值和叠加运算,再根据综合评价分级标准,得到矿山地质环境综合评价分区图。评价结果与实际调查情况相符,说明建立的评价指标体系较合理。研究成果对临武县矿山地质环境保护与生态文明建设具有重要的参考意义。  相似文献   

“云上贵州”平台下的市县国土资源信息整合实践与思考——以遵义市为例     

赵毅  李连凯  皮茂强  蒲云贵 《国土资源信息化》2017,(2)

“云上贵州”平台应用正在向市县国土资源部门延伸,贵州省“国土资源云”与贵州省“政务云”的横向信息资源整合进入实质性阶段,国土资源政务信息资源如何与当地政府信息资源整合,成为市县国土资源信息化面临的新课题.本文以遵义市为例,利用“云上贵州”平台信息资源整合的契机,实现市县国土政务信息资源跨部门、跨行业、跨平台的共享协同,逐步消除“信息孤岛”,促进国土资源决策科学化、监管精准化、服务便利化.  相似文献   

神农架林区西南坡局地暴雨过程诊断分析     

张福林  皮婷  张立军 《气象与环境科学》2017,40(2):100-108

神农架林区西南坡为局地暴雨灾害多发区。利用常规资料、多普勒雷达资料和区域自动站资料,分析了导致神农架林区西南坡2014年8月6日至7日夜间连续两场短时暴雨过程中MCS发生发展的天气背景及结构特征,并探讨了神农架山区复杂地形构造对西南坡暴雨的增幅作用。结果表明:1)中高层天气系统强迫弱时,副高边缘地面暖低压倒槽及850 h Pa气旋性弯曲区与辐合的发生发展可能是造成这类局地强降水天气的触发系统,地面弱冷空气的入侵有利于降水的维持和加强。2)两次局地暴雨过程均是由中β尺度对流系统影响产生的,降水历时短、强度大,雨区移动呈现局地性,具有明显的中尺度强对流系统特征,分别属前导层状云与尾随层状云中尺度对流系统型。3)第一场暴雨过程以对流降水为主,回波较强;第二场暴雨过程回波质心低且层状云特征比较突出,但维持时间相对较长,降水效率更高。4)神农架西南坡坡度大,海拔高度高,地形的动力抬升和辐合作用促使上升运动加强,地形强迫抬升作用显著不仅对局地对流触发、降水增幅有重要作用,而且会影响中尺度对流系统结构,这可能是神农架林区西南坡暴雨高发的重要原因。  相似文献   

水上钻孔灌注桩施工工艺   总被引：3，自引：0，他引：3  

皮跃进 《福建地质》2001,20(1):53-56

水上钻孔灌注桩施工应根据水底地质地貌情况，解决好护筒的选型、止漏、埋设、吊拔以及水中桩身的保护。  相似文献