一种基于MAD改进的GNSS高程时间序列粗差探测方法

针对GNSS高程时间序列中不可避免地含有粗差,以及在非线性、不平稳性的高程时间序列中粗差难以探测的问题,在传统MAD方法基础上,构建一种引入小波分析的WT-MAD粗差探测方法.利用模拟数据和LHAZ、BJFS、TWTF三个IGS站的实测高程数据进行实验,将WT-MAD法与基于最小二乘的3σ法、IQR法和MAD法进行对比...     

Zn, Pb, Cu and As distribution patterns in overbank and medium-order stream sediment samples: their use in exploration and environmental geochemistry

Overbank and medium-order stream sediment samples were collected in Belgium and Luxembourg from 66 sampling locations (area of about 33,000 km²) and analysed for major and trace elements among which Zn, Pb, Cu and As. At each sampling location large bulk samples were taken, namely in the lower (normally at ≥1.5 m depth, over an interval of about 20–40 cm) and upper (normally upper 5–25 cm) parts of the overbank profiles and from the stream sediments. Furthermore, at a number of these sites, a detailed geochemical analysis of vertical overbank sediment profiles (sampling intervals of 10–20 cm) was subsequently carried out to unravel element variations through time and to help in the overall evaluation. For most sampled sections evidences such as ¹⁴C-dating and the absence of anthropogenic particles point towards a pre-industrial and often pristine origin of the lower overbank sediment samples. From the latter bulk samples, mean background concentrations were deduced. They reveal the existence of significant differences between the northern and southern part of Belgium (incl. Luxembourg) which relate to the difference in geological substrate. In the north dominantly non-lithified Quaternary and Tertiary sands, marls and clays occur while in the south Palaeozoic sandstones, shales and carbonate rocks outcrop. Consequently separate mean background values were calculated for the two areas. In the southern study area, some anomalous metal concentrations have been recorded in pre-industrial sediments. They are derived from mineralised Palaeozoic rocks, a feature which could be of interest for base metal exploration. In the upper overbank and stream sediments, in general, higher heavy metal and As contents were recorded with highest values in areas with metal mining, metal melting and cokes treatment industries. By comparing the trace element concentrations of the upper overbank or stream sediment samples with the concentrations detected in the lower overbank samples at each of the sampling locations, and by evaluating the vertical distribution patterns where available, the degree of pollution of the alluvial plain and the present-day stream sediments can be assessed. From this exercise, it is clear that highest pollution occurs in the northern part of Belgium, which relates to its high population density and industrial development.     

A new approach to the Nd residence time in the ocean: the role of atmospheric inputs

Concentrations of rare earth elements (REE) and Nd isotopic ratios were analyzed for seawater, filtered suspension and sediment trap samples collected in the tropical Atlantic Ocean (EUMELI program, EUtrophic, MEsotrophic and oLIgotrophic sites, 20°N, 18°–21°W). This is the first REE/Nd dataset on solution and different-sized particles collected at the same site. We present direct evidence of the Nd isotopic exchange between particulate lithogenic fraction and seawater without significant mass transfer. This exchange is probably one of the main factors that simultaneously constrains the Nd concentration and isotopic ratio budget. We propose a new approach to estimate the residence time of Nd in the ocean (τ_Nd) based on isotopic exchange: 200 yr < τ_Nd< 1000 yr. The exchange requires a partial dissolution of lithogenic Nd. We estimate that the fraction of soluble Nd proportion in atmospheric dust is of the order of 20% based on the isotopic ratios. We suggest that the partial dissolution of atmospheric fallout is probably one of the main REE sources of the ocean.     

用连续小波变换分析探地雷达回波信号

脉冲探地雷达回波信号是典型的非平稳、非线性信号.本文通过连续小波变换,对地下圆柱目标实测结果进行分析,得到了目标冲击响应的典型波形特征.分析结果证明,这种方法可以有效地用于目标检测,时延估计等脉冲探地雷达信号处理中的关键问题     

清流玮埔地区花岗岩的时代和岩石序列

清流玮埔岩体曾是福建省印支期代表性岩体之一,出露有一定规模,前人把它作为单一的具片麻状构造黑云母二长花岗岩,在１：５万嵩口坪等４幅侵入岩调查中,全面采用侵入岩岩石谱系调查的新理论和新方法,对该岩体进行详细解体,划分出４１个侵入体,建立７个单元,将其归并为廖武坪序列,玮埔单元,盘兰溪序列,并确定了志留纪,三叠纪和晚侏罗纪３个时期的岩浆活动,在对该岩体的时代划分基础上,对不同时代岩石序列,岩石化学,地     

现代中国人起源的实证──颅骨特征的时空变化

本文用数学方法系统地检测了从早期智人到现代人时期中国人颅骨测量性特征的时空变化规律。结果显示,从早期智人到晚期智人的演化过程出现逆向变化、不连续;同时,长江以北的和长江以南的颅骨特征时态变化趋势也呈现显著差异。这两种现象的存在,揭示了现代北方的和南方的中国人可能由各自地区的早期智人演化而来。     

Analytical and Numerical Modeling of a Double Well Capture Zone

Closed-form steady-state analytical solutions for capture times are derived considering both pumping–injecting and pumping–pumping double-well systems. Numerical simulations are used to obtain capture times and the numerical results agree with analytical solutions. The influences of regional flows upon the capture zones are analyzed numerically. In a heterogeneously stratified aquifer, the mean and the variance of the capture time are calculated. It is found that hydraulic conductivity distribution plays an important role in determining the mean and the variance of the capture time.     

深海底钻机自动接杆卸杆储管机构

本文介绍了一种深海底使用的钻杆钻具储管机构的工作原理和结构特点。按照深海底钻孔工艺,设计了自动接杆、卸杆、存储机构。这一种机构采用两个单排转笼式储管架,分别存放钻杆和钻具管组件。每一个储管架各配备一双机械手,用于夹持钻杆和钻具在孔口位和储管架管口位之间的移送和卡紧定位。该机构可靠性高,取心率高,结构简单,方便操作。     

我国铁路水害及其评估模型研究

文章分析了我国铁路水害的特点,并用1980~1995年的断道时间和次数与同期的大雨、暴雨日数,分别建立了全国和成都、郑州、哈尔滨、沈阳4个铁路局的铁路水害统计模型,为定量评估气候异常对铁路交通的影响奠定了基础。     

江苏省小麦播种期的干旱研究及应用

本文确定了以降水量和蒸散量为参数的干旱指数计算方法,以小麦适宜播种期及前后各一句的时间范围内综合考虑各旬干旱指数,确定干旱指标,并讨论了江苏省小麦播种期干旱的发生规律。