Investigation of OMA formation and the effect of minerals   总被引：1，自引：0，他引：1  

Haiping Zhang  Ying Zheng  Kenneth Lee  Joseph V. Mullin 《Marine pollution bulletin》2010,60(9):1433-1441

Oil-mineral-aggregates (OMA) have been shown to be effective in oil spills cleanup. Experimental work was carried out to study the effects of physical-chemical properties of natural minerals and chemically modified minerals on OMA formation and oil removal. The results showed that the hydrophobicity, particle sizes and specific surface of minerals played an important role in OMA formation. Appropriate hydrophobicity of minerals can enhance the formation of OMA. The surface property of minerals can also influence the shape of OMA. Spherical mineral-oil aggregates were frequently formed with hydrophilic minerals while irregular shaped OMA were observed with hydrophobic minerals. The sizes of OMA also increased when the minerals changed from hydrophilic to hydrophobic. The effects of dispersant and mixing energy were also carefully studied. The results showed that dispersant were a dominant factor. When dispersant was applied, effects of other factors became minimal.  相似文献   

基于MRPs无陀螺卫星姿态确定的抗差估计算法     

牟忠凯  隋立芬  曹轶之 《大地测量与地球动力学》2010,30(1):104-108

针对精确航天器姿态问题,采用修正罗德里格参数(MRPs)表示姿态,用动力学方程进行角速率的传播,分别基于等价协方差和观测残差统计特性的协方差调整方法,实现UKF算法的抗差效果,并通过仿真验证该方法的有效性。仿真结果表明：在含有粗差的情况下,两种抗差UKF算法均能得到稳定的状态估计值,而第二种方法计算效率更高。  相似文献   

利用改进的SRTI法研究中尺度电离层行波扰动   总被引：1，自引：1，他引：0       下载免费PDF全文

张小红  唐龙  郭博峰 《地球物理学报》2013,56(12):3953-3959

针对现有单站电离层行波扰动指数(Single Receiver TID Index,SRTI)探测中尺度电离层行波扰动时探测周期范围有限的问题,本文提出了一种改进的SRTI方法,以提高探测扰动周期的适用范围.介绍了利用SRTI和改进的SRTI探测中尺度电离层行波扰动的原理,从理论上分析比较了二者探测扰动周期范围的能力,并采用美国加州南部的5个IGS站2012年年积日189的GPS观测数据,对电离层扰动进行了分析.结果显示在21∶30—23∶00LT时,扰动观测序列存在周期为15min和39min的扰动波,但是现有SRTI方法只探测到了前者,而改进的SRTI法很好地探测到了两个周期的扰动波,表明其对短周期和较长周期的扰动均具有较好的灵敏性.利用改进的SRTI法计算的扰动观测序列,应用傅里叶变换相位差分法估计了电离层扰动的传播参数,其结果总体上与前人研究成果一致,这表明改进的SRTI法完全可以应用于电离层行波扰动的研究中,而且由于计算简单,在处理大量数据时具有一定优势.  相似文献   

GPS多路径效应中的EEMD时空滤波器     

徐佳  杨秋实  杨帆 《测绘科学》2013,38(3):57-58,62

根据结构动态监测中GPS多路径效应的日重复性和低频周期等特性,本文研究了一种基于集成经验模态分解(EEMD)技术的滤波方法,构造了EEMD时空滤波器。通过计算连续两天GPS动态监测数据EEMD的相关系数,提取GPS监测数据中的多路径效应。实验结果表明了该方法的有效性,为结构动态变形模态分析提供了有效数据。  相似文献   

Effects of Salt on Microbial Populations and Treatment Performance in Purifying Saline Sewage Using the MUCT Process     

《洁净——土壤、空气、水》2009,37(8):649-656

  相似文献   

Some modifications of Stokes' formula that account for truncation and potential coefficient errors   总被引：1，自引：1，他引：0  

L. E. Sjöberg  A. Hunegnaw 《Journal of Geodesy》2000,74(2):232-238

 Stokes' formula from 1849 is still the basis for the gravimetric determination of the geoid. The modification of the formula, originating with Molodensky, aims at reducing the truncation error outside a spherical cap of integration. This goal is still prevalent among various modifications. In contrast to these approaches, some least-squares types of modification that aim at reducing the truncation error, as well as the error stemming from the potential coefficients, are demonstrated. The least-squares estimators are provided in the two cases that (1) Stokes' kernel is a priori modified (e.g. according to Molodensky's approach) and (2) Stokes' kernel is optimally modified to minimize the global mean square error. Meissl-type modifications are also studied. In addition, the use of a higher than second-degree reference field versus the original (Pizzetti-type) reference field is discussed, and it is concluded that the former choice of reference field implies increased computer labour to achieve the same result as with the original reference field. Received: 14 December 1998 / Accepted: 4 October 1999  相似文献   

Removal of selected metals from drinking water using modified powdered block carbon     

V. Campos  I. J. Sayeg  P. M. Buchler 《Environmental Geology》2008,55(5):1023-1028

This paper presents the possible alternative removal options for the development of safe drinking water supply in the trace elements affected areas. Arsenic and chromium are two of the most toxic pollutants, introduced into natural waters from a variety of sources and causes various adverse effects on living bodies. Performance of three filter bed method was evaluated in the laboratory. Experiments have been conducted to investigate the sorption of arsenic and chromium on carbon steel and removal of trace elements from drinking water with a household filtration process. The affinity of the arsenic and chromium species for Fe/Fe₃C (iron/iron carbide) sites is the key factor controlling the removal of the elements. The method is based on the use of powdered block carbon (PBC), powder carbon steel and ball ceramic in the ion-sorption columns as a cleaning process. The PBC modified is a satisfactory and practical sorbent for trace elements (arsenite and chromate) dissolved in water.  相似文献   

基于EEMD方法的河南省倒春寒时空分布分析   总被引：1，自引：0，他引：1  

徐岩岩  常军 《气象与环境科学》2017,40(3):28-32

根据1961-2014年河南省100个站3-4月的逐日气温资料,以及河南省倒春寒标准,建立倒春寒发生次数的时间序列,采用集合经验模态分解(EEMD)、Mann-Kendall等方法研究了河南省倒春寒时空分布特征。结果表明,河南倒春寒发生次数基本上呈现出自西南向东北逐渐增多的空间格局,2~3级倒春寒发生次数呈现出北少南多的空间格局。河南整个中部地区发生倒春寒的总次数较多,并且也会发生较为严重的倒春寒。通过EEMD分析,IMF1模态和趋势项基本反映了倒春寒的演变规律。河南倒春寒的年发生次数有一个明显的准5 a周期振荡,且发生次数呈明显的减少趋势。2000年和2005年为突变点,在春季增暖的气候背景下倒春寒年发生次数开始减少。  相似文献   

The AUSGeoid98 geoid model of Australia: data treatment, computations and comparisons with GPS-levelling data     

W. E. Featherstone  J. F. Kirby  A. H. W. Kearsley  J. R. Gilliland  G. M. Johnston  J. Steed  R. Forsberg  M. G. Sideris 《Journal of Geodesy》2001,75(5-6):313-330

 The AUSGeoid98 gravimetric geoid model of Australia has been computed using data from the EGM96 global geopotential model, the 1996 release of the Australian gravity database, a nationwide digital elevation model, and satellite altimeter-derived marine gravity anomalies. The geoid heights are on a 2 by 2 arc-minute grid with respect to the GRS80 ellipsoid, and residual geoid heights were computed using the 1-D fast Fourier transform technique. This has been adapted to include a deterministically modified kernel over a spherical cap of limited spatial extent in the generalised Stokes scheme. Comparisons of AUSGeoid98 with GPS and Australian Height Datum (AHD) heights across the continent give an RMS agreement of ±0.364 m, although this apparently large value is attributed partly to distortions in the AHD. Received: 10 March 2000 / Accepted: 21 February 2001  相似文献   

肾脏CT扫描前准备工作的改进方法     

朱凤丽  李学芳 《CT理论与应用研究》1997,6(2):10-11

本文回顾分析１９８７年３月￣１９９２年５月行肾脏ＣＴ扫描１０２例，其中诊断肾结石３１，当时因ＣＴ扫描前准备方法问题，及开始经验不足造成４例无结石的病人误诊为结石。找到误诊石的原因是ＣＴ扫描前静脉试验及口服泛影葡胺造影剂造成，采取改进ＣＴ扫描前准备方法；（１）扫描前不行静脉试验（２）口服造影剂改为口服温水或牛奶，经上述改进方法，以后未出现造影剂造成肾结石误诊。  相似文献