Evaluation of a laser‐assisted particle sizing/settling velocity determination technique     

I. G. Droppo  B. G. Krishnappan  C. Jaskot 《水文研究》2006,20(9):1885-1893

The use of predictive models for the understanding and management of sediment and contaminant transport generally requires knowledge of particle size and settling velocity. Particle size is often obtained by direct measurements, and the settling velocities are usually predicted using the Stokes' law (or a modification thereof) for single‐grained spherical particles. Such measurements and estimates are not satisfactory measures for cohesive sediments, which exist as agglomerated particles called flocs and whose behaviour is significantly different from that of the single‐grained particles. Direct measurement of settling velocity and size using optical methods in settling columns has also been employed to improve these predictions; however, the subjectivity in determining which particles are in focus results in unreliable size data. An out‐of‐focus particle will generally possess a larger size than in reality. This paper evaluates a laser‐assisted particle sizing/settling velocity determination technique's ability to eliminate the subjectivity and improve particle‐sizing accuracy during settling column experiments. Although the diffraction of light by the translucent standard beads (used for evaluating the technique's accuracy for determining particle size) posed a problem, the results suggest that this technique has potential for assisting researchers to obtain the most accurate settling particle size data possible. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

激光法粒度筛析校正研究   总被引：1，自引：0，他引：1  

王慎文  谢春安  唐渊明  胡艳革 《沉积学报》2012,30(4):716-723

激光法和筛析法分析作为两种最常见的用于沉积地质粒度分析的方法,其间的数据转换校正是在数据对比、数据对接时经常遇到且无法回避的问题。为此设计了两个实验,实验一对比了窄粒度范围样品两种分析方法的分析结果,统计分析了筛析法比激光法偏大的幅度,并提出一个校正方法;实验二对不同磨圆程度的样品进行分析,研究了磨圆度与两种分析方法差异程度之间的相关关系,认为实验一提出的校正方法适合一般条件下的天然沉积物粒度分析校正。文章又以实例展示了所提出的校正方法的校正效果并讨论了激光粒度法存在的问题。激光粒度分析法用于天然沉积物粒度分析时,结果常见明显的光滑化、正态化、双峰合并现象,扭曲了真实的粒度分布。文章认为实际样品具体情况远远复杂于米氏理论的设定条件,样品条件参数并未全部带入计算过程,所以激光法粒度求解是不精确的。更好的数据校正方法有待于激光粒度仪的软件、硬件改进。激光法合理的用于天然沉积物粒度分析还有一些问题需要讨论。  相似文献   

麻江古油藏原生水晶中固体沥青包裹体的发现及地质意义   总被引：3，自引：2，他引：1  

刘劲松  马昌前  王世明  陈玲  李民 《地质科技情报》2009,28(6)

在麻江古油藏坝固地区,产于下奥陶统红花园组碳酸盐岩储层晶洞中的大部分水晶中均含有固体沥青包裹体,其中一类为水晶生长过程中捕获白云岩晶洞中的储层沥青,可能代表了传统上认为的在加里东期被破坏的麻江古油藏。激光拉曼光谱分析显示该类固体沥青包裹体与白云岩晶洞中的储层沥青都具有较高的演化程度。根据流体包裹体显微测温和埋藏史分析,认为麻江古油藏存在印支期成藏的油气,结合流体包裹体与水晶中原生固体沥青包裹体的共生关系,为传统认为的麻江古油藏在加里东期被破坏提供了新证据,此外,还对印支期成藏油气的来源做了初步分析。  相似文献   

三维激光扫描技术在双龙洞测量中的应用     

张磊  张泾文  胡震海 《岩土工程技术》2009,23(2):60-63

介绍了三维激光扫描技术在金华双龙洞测量中的应用情况。这一研究不仅提高了洞穴测量的工作精度和工作效率,还为洞穴内部地貌与地质体形态三维可视化构建、虚拟洞穴内部地理场景构建、洞穴地理信息系统建设提供数据源,为洞穴数据库建设、洞穴景观旅游开发、洞穴环境与景观保护、洞穴考古等提供直观精密的基础数据。  相似文献   

盐水溶液中常见阴离子团的激光拉曼光谱定量分析研究   总被引：7，自引：0，他引：7  

叶美芳  王志海  唐南安 《西北地质》2009,42(3):120-126

应用RenishawinVia激光拉曼光谱仪分析研究了人工配制的钠盐溶液中CO3 2-、SO4 2-、HSO4-、HCO3-和NO3-等阴离子团及水包络峰的拉曼谱图特征,建立了拉曼光谱参数（强度面积积分）与溶液中阴离子团浓度的定量关系,提出了利用拉曼谱峰强度面积分法定量分析流体包裹体中CO3 2-、SO4 2-、HSO4-、HCO3-和NO3-等常见阴离子团浓度的方法。对HSO。一和HCO。一这样易电离的酸式阴离子团采用了净目标酸式阴离子团浓度拟合工作曲线。讨论了强度面积积分法定量分析的优越性和激光拉曼探针定量分析Cl-的难点及前景。  相似文献   

基于投影点密度的车载激光扫描距离图像分割方法   总被引：16，自引：0，他引：16  

史文中  李必军  李清泉 《测绘学报》2005,34(2):95-100

对车载激光扫描系统获取的距离图像的分割进行研究,提出利用投影点密度进行距离图像分割的方法.该方法不需要其他辅助数据就可以进行距离图像的分割,给出应用实例.图像的分割是目标识别、定位、特征提取与建模的基础和关键.距离图像是离散坐标点阵列,不表达目标边界特征和拓扑关系,到目前为止还没有距离图像分割的成熟、可行方法.本文研究成果,展现了激光扫描技术在数据获取、处理研究上的新方向.  相似文献   

三维激光扫描仪及其测量误差影响因素分析   总被引：30，自引：0，他引：30  

郑德华  沈云中  刘春 《测绘工程》2005,14(2):32-34,56

回顾了近年来三维激光扫描技术及其测量误差方面的研究成果,将三维激光扫描技术分为径向三维激光扫描仪、相位干涉法扫描系统和三角法扫描系统三种类型.从仪器误差、与目标物体反射面有关的误差和外界环境条件影响三个方面,分析了三维激光扫描系统误差影响.  相似文献   

Evaluation of CHAMP satellite orbit with SLR measurements   总被引：1，自引：0，他引：1  

QIN Xianping YANG Yuanxi 《地球空间信息科学学报》2005,8(3):209-213

The technique of Evaluating CHAMP satellite orbit with SLR measurements iS presented. As an independent evaluation of the orbit solution, SLR data observed from January 1 to 16, 2002 are processed to compute the residuals after fixing the GFZ＇s post science orbits solutions. The SLR residuals are computed as the differences of the SLR measurements minus the corresponding distances between the SLR station and the GPS-derived orbit positions. On the basis of the SLR residuals analysis, it is found that the accuracy of GFZ＇ s post science orbits is better than 10 cm and that there is no systematic error in GFZ＇s post science orbits.  相似文献   

Close-range terrestrial digital photogrammetry and terrestrial laser scanning for discontinuity characterization on rock cuts   总被引：9，自引：0，他引：9  

M. Sturzenegger  D. Stead 《Engineering Geology》2009,106(3-4):163-182

This paper reviews the application of close-range terrestrial digital photogrammetry and terrestrial laser scanning for discontinuity characterization on rock cuts. Terrestrial remote sensing techniques are being increasingly used as a complement to traditional scanline and window mapping methods. They provide more comprehensive information on rock cuts, allow surveying of inaccessible outcrops, and increase user safety. Selected case studies are used to estimate the accuracy of several 3D model registration approaches and the most time-, effort- and cost-effective methods are highlighted. It is shown that simple registration networks are able to provide adequate measurement of discontinuity orientation for engineering purposes. The case studies presented also illustrate the effects of sampling bias and limitations related to discontinuity characterization using remote sensing techniques. Vertical orientation bias and occlusion can be of particular concern when persistent discontinuities dip at the same angle as the camera/scanner line-of-sight. Major advantages of the techniques are presented illustrating how terrestrial remote sensing techniques provide rapid spatial measurements of discontinuity location, orientation and curvature and are well suited to the quantification of persistence magnitudes greater than 3 m.  相似文献   

Matrix-independent Fe isotope ratio determination in silicates using UV femtosecond laser ablation     

Grit Steinhoefel  Ingo Horn  Friedhelm von Blanckenburg 《Chemical Geology》2009,268(1-2):67-73

UV femtosecond laser ablation coupled to MC-ICP-MS provides a promising in situ tool to investigate elemental and isotope ratios by non-matrix-matched calibration. In this study, we investigate Fe isotope composition in siliceous matrices including biotite, hornblende, garnet, fayalite and forsterite (San Carlos Olivine), and an oceanic Fe–Mn crust using the iron reference material IRMM-014 for calibration. To test the accuracy of the laser ablation data, Fe isotope compositions were obtained independently by solution ICP-MS after chromatographic separation of Fe. Sample materials with low Cr content, i.e. biotite, hornblende, fayalite and the Fe–Mn crust, reveal δ^56/54Fe and δ^57/54Fe values that agree with those from solution ICP-MS data within the measured precision. For high Cr concentration (⁵⁴Cr/⁵⁴Fe >0.0001), i.e. in the garnet and forsterite sample, δ^56/54Fe and δ^57/54Fe values were derived from ⁵⁷Fe/⁵⁶Fe ratios as correction of the isobaric interference of ⁵⁴Cr on ⁵⁴Fe is unsatisfactory. This approach provides accurate results for both minerals. Moreover, the garnet crystal exhibits isotopic zonation with differences of 0.3‰ in δ^56/54Fe showing that substantial heterogeneities exist in high-temperature metamorphic minerals. Multiple analyses of homogeneous sample materials reveal a repeatability of 0.1‰ (2 SD) for δ^56/54Fe and 0.2‰ (2 SD) for δ^57/54Fe, respectively. This study adds to the observations of Horn et al. (2006) who have shown that the determination of Fe isotope ratios in various matrices including iron alloys, iron oxides and hydroxides, iron sulfide and iron carbonates can be performed with high accuracy and precision at high spatial resolution using UV femtosecond laser ablation ICP-MS. These results demonstrate that femtosecond laser ablation ICP-MS is a largely matrix-independent method, which provides a substantial advantage over commonly employed nanosecond laser ablation systems.  相似文献