红沿河核电站取水口海冰堆积特性的离散元分析

在寒冷地区,海冰在核电站取水结构物前的堆积会对取水口造成阻塞和损坏,进而影响核电设备的正常运作。以红沿河核电站的取水设施为例,综合考虑该工程海域冰区特点及风和流的作用等因素。建立了海冰的离散元模型,用于模拟海冰在结构物前的堆积和破坏过程。该离散元模型由规则排列的球体颗粒构成,颗粒间采用平行黏结模型进行黏结。考虑了海冰的平均尺寸、密集度及流速三个因素对海冰堆积过程的影响,对海冰堆积高度进行预判。其中,堆积高度随海冰的密集度和流速的增大而增大,而海冰的平均尺寸对堆积高度没有明显影响。分析结果表明,离散元数值模拟可用于评估和预测取水工程中海冰堆积造成堵塞的风险。     

深埋长隧道TBM施工关键问题探讨

针对深埋长隧道开挖所面临的高水压、高地压、高地温、大变形、难支护等问题,分析总结传统钻爆法开挖与支护技术、全断面隧道掘进机（TBM）施工技术、TBM导洞扩挖技术应用中的优劣,TBM导洞扩挖法为深埋长隧道开挖提供了新的设计思路。由于深埋长隧道的建设环境与浅埋隧道建设环境存在显著差异,TBM施工将面临3个关键问题--岩爆问题、卡盾（大变形）问题和未准确探测前方地质而发生的施工事故（涌水、突泥等）。为揭示TBM施工过程中卡盾的存在性,分别针对某一特定地质条件下深埋软、硬岩TBM施工进行理论分析和数值模拟研究。结果表明,软岩地层TBM施工发生卡盾,而硬岩完整地层TBM施工未发生卡盾。     

FHD分量核旋仪观测系统的抗干扰技术

空间电磁波干扰和电源高频谐波干扰是分量核旋仪观测系统的主要干扰源;分量核旋仪观测系统的探头、分量线圈、供电系统及通信线路是主要的干扰途径。作者着重对干扰途径进行了分析,提出了观测系统的抗干扰措施,并分别对探头及信号输入通道、分量线圈、供电系统、通信线路、仪器电路、仪器控制软件进行了全方位的抗干扰设计,新设计提高了分量核旋观测系统的抗干扰能力。     

GPS抗干扰方法综述

全球定位系统提供的低能级信号易受干扰。这些干扰或对抗导致GPS丢失信息，因而成为威胁GPS的严重问题。本文探讨对抗或干扰对GPS的威胁，从策略，干扰源和GPS接收机角度谈抗干扰方法，侧重分析减少GPS干扰的技术。     

GPS抗干扰

最近几次大的局部战争中，全球定位系统GPS（Global Positioning System）受到了越来越多的关注，它已经成为现代战争的又一块重要领域。即使在民用领域，从天上飞行的航班、地上急驰的车辆、海上游弋的船只到宏物小狗脖子上戴的跟踪器，GPS是无时无刻都在发挥着重要作用。目前，欧共体兴致勃勃地组建Galileo导航系统，并希望能在未来的全球导航卫星系统GNSS（Global Navigation Satellite System）唱主角。我国在2000年也成功发射了两颗“北斗“导航试验卫星。这些再加上俄罗斯那苦苦支撑的GLONASS，使得GPS发展及其相关议题变得越来越引人注目。本文重点介绍了一些针对GPS干扰的措施和技术，指出了这些措施和技术的优点和不足。另外，GPS系统构成、工作原理及干扰形式在此亦有所涉及。     

谈液动冲击回转钻进技术在破碎岩层中运用

简要说明液动冲击回转钻进是一项投资少,见效快的先进适用的钻探技术,可大幅度提高钻探效率和经济效益,增加回次长度和岩矿芯采取率,并能减少孔内事故。     

对依兰煤田钻孔缩径挤夹钻具事故的认识

针对依兰煤田钻探施工中出现的钻孔缩径挤夹钻具事故,提出产生事故的根本原因不是因岩层本身膨胀所致,而是由于某种岩层裂隙发育,渗透性良好,吸水性强,使钻孔孔壁泥皮迅速增厚所致,并提出预防事故的具体措施。     

Sediment jamming of a trunk stream by hyperconcentrated floods from small tributaries: case of the Upper Yellow River,China

ABSTRACT

The tributary–trunk stream relationship is investigated with respect to hyperconcentrated flows and coupled wind–water processes in the Yellow River, China. Ten small tributaries that drain only 3% of the total drainage area of the trunk stream transport large amounts of relatively coarse sediment from the desert to the trunk stream during hyperconcentrated floods. The resultant strong sedimentation often jams the trunk stream, leading to serious disasters. This study reveals the cause of this interesting phenomenon and proposes countermeasures for disaster reduction. A typical sediment-jamming event (SJE) in July 1989 was thoroughly analysed based on the observational data, including the beginning, development and final stages of the event. An index of the geomorphologic effectiveness of the tributary on the trunk stream and a number of indices describing SJEs and the influencing factors are adopted, based on which a discrimination relationship for the occurrence of SJEs is established and some statistical relationships are also established. The SJE’s hydrological and geomorphologic impacts are discussed at short timescales (from several days to one month) and at long time scales (up to 46 years). The results may help to gain a new insight into the study of the tributary–trunk stream relationship, and provide useful information for sediment management and disaster-reduction planning in the drainage basin. Countermeasures are suggested to reduce the channel sedimentation and the risk of sediment-jamming disaters.

Editor M.C. Acreman Associate editor Q. Zhang     

ICA在合成孔径雷达抗噪声干扰中的应用研究

将ICA（Independence Component Analysis）消噪原理应用于合成孔径雷达抗噪声干扰技术中,用噪声信号和受到干扰的SAR回波数据作为扩展的虚拟观测信号,对扩展的多维加噪观测信号进行分离, 得到源雷达回波信号, 从而实现噪声的有效消除.通过对条带式SAR点目标成像进行仿真试验, 结果表明这种消噪方法在消除SAR噪声干扰中是有效的.     

Inundation extent as a key parameter for assessing the magnitude and return period of flooding events in southern Iceland

Abstract

River flow conditions in many watersheds of Iceland are particularly disturbed during winter by the formation, drifting and accumulation of river ice, whose impact on water encroachment and extent of inundations is not reflected in the discharge records. It is therefore necessary to use river discharge with great caution when assessing the magnitude of past inundations in Iceland, and to give attention to other flood magnitude parameters. A GIS-based methodology is presented that focuses on inundation extent as an alternative parameter for the assessment and ranking of the magnitude of past flooding events in the Ölfusá-Hvítá basin, known as one of the most dangerous flood-prone river complexes in Iceland. Relying ultimately on a macro-scale grid, the method enabled the reconstruction of the extent of inundations, the delineation of the flood plain, and, finally, some estimation of the likelihood of flooding of exposed areas that include marine submergences and river floods for both open water and ice conditions.

Citation Pagneux, E., Gísladóttir, G. & Snorrason, Á. (2010) Inundation extent as a key parameter for assessing the magnitude and return period of flooding events in southern Iceland. Hydrol. Sci. J. 55(5), 704–716.