共查询到20条相似文献，搜索用时 15 毫秒
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主要阐述了隧道断面测量仪及激光测距技术,从激光测距的原理入手,探讨高精度测距系统的研究,从而解决困扰隧道工程界的非接触监测断面收敛的难题。 相似文献
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Laser microprobe (U-Th)/He geochronology 总被引：3，自引：0，他引：3
J.W. Boyce K.V. Hodges M.J. Jercinovic P.W. Reiners 《Geochimica et cosmochimica acta》2006,70(12):3031-3039
A new analytical method had been developed to enable high-spatial-resolution (U-Th)/He dating of accessory minerals. It involves the use of a focused ArF excimer to ablate pits in a polished grain surface, with the evolved gases spiked for isotope-dilution measurement of radiogenic 4He. These data are converted to concentrations by precise measurement of each pit using an optical interferometric microscope. U, Th, and Sm concentration measurements are made using one of several alternative microanalytical techniques (e.g., wavelength-dispersive electron microprobe analysis or laser-ablation, inductively coupled plasma mass spectrometry). By way of illustration, we present both conventional and laser microprobe (U-Th)/He dating results for a Brazilian monazite sample. Laser microprobe data (28 measurements on two crystal fragments) yield a weighted mean (U-Th)/He date of 455.3 ± 3.7 Ma (2SE). This result is statistically indistinguishable from the mean conventional (U-Th)/He date for three separate grain fragments: 449.6 ± 9.8 Ma (2SE). The agreement of conventional and laser ablation dates should encourage a wide variety of applications of the technique, including: (1) detrital mineral dating for provenance and unroofing studies; (2) the dating of broken, included, highly zoned, or irregular grains which are not easily corrected for α-ejection; and (3) measuring 4He loss profiles that can be inverted to determine cooling histories. 相似文献
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目前我国的许多古建筑维修、保护工程中缺少建筑物结构图、破坏程度评估困难等问题,因此急需一种快速而全面的建筑物测量手段。三维激光扫描技术作为一种快速、非接触、高精度的测量方法,满足古建筑维修保护中的测量要求。本文通过研究三维激光扫描测量技术在古建筑维修与保护工程中的使用案例,讨论该技术在我国古建筑维修保护中的使用方式与方法,详细介绍三维激光用于古建筑扫描中的勘查、实施、点云处理及建模中的具体步骤和注意事项。本文的介绍有助于汶川大地震后四川和我国其他地区古建筑维修保护工程中对建筑物测量的实施。 相似文献
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Paul J. Sylvester 《Geostandards and Geoanalytical Research》2005,29(1):41-52
This annual review of laser-ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS) covers the year 2003. Significant advances were made in understanding laser-sample interactions. In particular, research defined the distribution of particle sizes produced by the interplay of laser wavelength, laser pulse width and the gas environment of ablation. A link between particle sizes and elemental and isotopic fractionation at both the ablation site and in the ICP was established. Experimental 15 7 nm and femtosecond laser systems were tested with promising results. The number of applications of LA-ICP-MS in geology and environmental Earth science continued to grow with particular interest in element concentration and isotope ratio profiling of materials, linking composition to time scales. In situ isotopic ratio measurements were increasingly made using multicollector magnetic sector ICP-MS instruments. Other applications of wide interest included bulk sampling of rocks and ores prepared as lithium borate glasses; low level analysis of platinum-group elements, rhenium and gold in sulfides, metal and silicates; in situ uranium-lead zircon geochronology; and melt and fluid inclusion analysis. 相似文献
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激光加工技术在珠宝首饰业中的应用越来越广泛。介绍了该技术的基本特点以及其在珠宝首饰业中的典型应用现状。这些技术涉及激光焊接、激光快速原型技术、激光打标、激光雕刻和激光切磨钻石等领域。激光焊接比传统的焊接技术具有显著的优点;快速原型技术的引入大大缩短了从首饰图样到制出原版的时间;激光打标和激光雕刻的使用丰富了首饰表面处理的手段,可进一步满足首饰个性化需求;激光切磨钻石原石可达到最小的损耗。激光加工技术在珠宝首饰业中发挥着越来越重要的作用。 相似文献
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A preliminary test of biogeochemical exploration for locating uranium occurrences in the Marfa Basin, Texas, was conducted in 1978. Only 6 of 74 plant samples (mostly catclaw mimosa, Mimosa biuncifera) contained uranium in amounts above the detection limit (0.4 ppm in the ash) of the conventional fluorometric method. The samples were then analyzed using a Scintrex UA-3 uranium analyzer* - an instrument designed for direct analysis of uranium in water, and which can be conveniently used in a mobile field laboratory. The detection limit for uranium in plant ash (0.05 ppm) by this method is almost an order of magnitude lower than with the fluorometric conventional method. Only 1 of the 74 samples contained uranium below the detection limit of the new method. Accuracy and precision were determined to be satisfactory. Samples of plants growing on mineralized soils and nonmineralized soils show a 15-fold difference in uranium content; whereas the soils themselves (analyzed by delayed neutron activation analysis) show only a 4-fold difference. The method involves acid digestion of ashed tissue, extraction of uranium into ethyl acetate, destruction of the ethyl acetate, dissolution of the residue in 0.005% nitric acid, and measurement. 相似文献
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《Physics and Chemistry of the Earth, Part A: Solid Earth and Geodesy》1999,24(7):563-567
A methodology is presented that shows how Confocal Scanning Laser Microscopy (CSLM) can be used to measure the microscopic three dimensional distribution of pore bodies and pore throat size in sandstones with hydrocarbon reservoir potential. The technique involves injection of doped epoxy into the sample pore space, followed by non-destructive serial sectioning of the rock using laser light. Fluorescence imaging combined with image thresholding techniques allows the pore volume structure of the sample to be reconstructed to a depth of > 500 microns. The main problems encountered during experimentation were degraded depth resolution and laser attenuation, both of which contributed to inaccuracies in the sample image. Using a method of ‘point-wise thresholding’ these technical difficulties can be overcome, allowing a highly accurate volume reconstruction to be made. Accounting fully for laser attenuation will in principle allow a reduction in the amount of injected fluorochrome concentration, and thus deeper depth penetration and imaging of the sample. Euclidean distance maps are suggested as a means of addressing the shortcomings in classical medial axis transforms for application to connectivity investigations. 相似文献
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激光熔蚀微量氧同位素分析方法及其地质应用 总被引：2，自引：1，他引：1
研究小尺度或微区的同位素组成变化已成为地球化学分析技术发展的重要方向之一。在研制CO2激光熔蚀氧同位素制样装置的基础上,通过该装置与MAT253质谱计联机实现了硅酸盐和氧化物矿物的氧同位素在线分析。所测样品包括NBS28石英标样、石英玻璃,以及天然的石榴子石、锆石、橄榄石等一些难熔矿物。该装置分析的颗粒样品氧同位素分析精度为±022‰,最低样品量为8μmol的O2;石英玻璃原位分析的氧同位素分析精度为±035‰,最低样品量为7μmol的O2。这种装置和分析方法具备速度快,熔样温度高的特点,尤其适于难熔矿物。该装置可采用脉冲激光实现石英玻璃的微区原位分析,可应用于单个矿物生成环带的氧同位素研究。 相似文献
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激光显微光谱分析法目前在地质、冶金、国防等科学和技术领域里得到了广泛应用,它已成为物质微区化学成份分析的一种重要手段。要使激光显微光谱分析法能迅速的发展,必须解决当前分析上存在的标样的制 相似文献
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基于三维激光扫描的空间地物建模 总被引：4，自引：0，他引：4
利用地面三维激光扫描仪获取的空间数据,进行了三维空间地物建模研究。以建筑物建模为例,首先从原始数据中分离提取建筑物,然后对得到的建筑物数据进行去噪处理,再通过整体匹配纠正并对原始测量数据进行重新采样和拼接配准,建立了由三角网构成的三维表面模型。结果表明,所构建的三维表面模型较好地表达了建筑物的几何特征,户外实验也验证了上述过程可以实现对建筑物快速三维建模。 相似文献
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Jan Kosler Mike N. Tubrett Paul J. Sylvester 《Geostandards and Geoanalytical Research》2001,25(2-3):375-386
Recent advances in laser ablation ICP-MS techniques allow accurate U-Th-Pb age dating of monazites that are as young as several tens of million years to a precision better than 2%. Accuracy of the age determinations has been improved by true real-time mass bias correction via nebulisation of a solution containing enriched 233 U and natural Tl isotopes. The Tl-U tracer solution eliminates possible effects of variable sample matrices on the precision and accuracy of measured isotopic ratios. Mass bias corrections based on measured 205 Tl/233 U ratios in the tracer solution allow direct measurement of 235 U in monazite. Combined with high-sensitivity laser ablation ICP-MS measurements, direct measurement of 235 U particularly improves the precision of U-Pb dating of young monazites. Correction for laser-induced Pb/U and Pb/Th elemental fractionation is based on a mathematical treatment of time resolved count-rate data that is independent of laser ablation characteristics, does not require external standardisation and allows variable laser pit size or raster patterns for each measurement. The new procedures make the LA ICP-MS technique more flexible for in situ U-Th-Pb analysis. 相似文献
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一种机载雷达点云数据的快速分类方法 总被引：1，自引：0，他引：1
机载激光雷达扫描技术可以以点云形式快速获取地形表面高精度三维信息。基于激光雷达扫描数据及建筑物本身的拓扑信息就可以对建筑物进行精确的重建,而重建中最关键的技术是对点云数据进行分类,进而进行地物识别。对大规模三维点云数据进行快速分类,提出一种采用区域分割结合基于最小二乘平差的多项式拟合方法,将大量离散的三维点云分割后进行多项式拟合,并将二维数据分类转化为一维数据分类。在分类的基础上,将建筑物几何规则作为约束条件提取了房屋边缘。实验分析表明,该方法既能去除多余噪声,又能有效保留特征点,分类的总误差率低于3%。 相似文献
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Daniel A. Frick Jan A. Schuessler Michael Sommer Friedhelm von Blanckenburg 《Geostandards and Geoanalytical Research》2019,43(1):77-91
Silicon is a beneficial element for many plants and is deposited in plant tissue as amorphous bio‐opal called phytoliths. The biochemical processes of silicon uptake and precipitation induce isotope fractionation: the mass‐dependent shift in the relative abundances of the stable isotopes of silicon. At the bulk scale, δ30Si ratios span from ?2 to +6‰. To further constrain these variations in situ, at the scale of individual phytolith fragments, we used femtosecond laser ablation multi‐collector inductively coupled plasma‐mass spectrometry (fsLA‐MC‐ICP‐MS). A variety of phytoliths from grasses, trees and ferns were prepared from plant tissue or extracted from soil. Good agreement between phytolith δ30Si ratios obtained by bulk solution MC‐ICP‐MS analysis and in situ isotope ratios from fsLA‐MC‐ICP‐MS validates the method. Bulk solution analyses result in at least twofold better precision for δ30Si (2s on reference materials ≤ 0.11‰) over that found for the means of in situ analyses (2s typically ≤ 0.24‰). We find that bushgrass, common reed and horsetail show large internal variations up to 2‰ in δ30Si, reflecting the various pathways of silicon from soil to deposition. Femtosecond laser ablation provides a means to identify the underlying processes involved in the formation of phytoliths using silicon isotope ratios. 相似文献
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Matthijs C. van Soest Brian D. Monteleone Jeremy W. Boyce 《Geochimica et cosmochimica acta》2011,75(9):2409-161
Ultraviolet lasers coupled with sensitive mass spectrometers provide a useful way to measure laboratory-induced noble gas diffusion profiles in minerals, thus enabling the calculation of diffusion parameters. We illustrate this laser ablation depth profiling (LADP) technique for a previously well-studied mineral-isotopic system: 4He in Durango fluorapatite. LADP studies were conducted on oriented, polished slabs from a single crystal that were heated under vacuum to a variety of temperatures between 300 and 450 °C for variable times. The resolved 4He profiles exhibited error-function loss as predicted by previous bulk 4He diffusion studies. All of the slabs, regardless of crystallographic orientation, yielded modeled diffusivities that are statistically co-linear on an Arrhenius diagram, suggesting no diffusional anisotropy of 4He in this material. The data indicate an activation energy of 142.2 ± 5.0 (2σ) kJ/mol and diffusivity at infinite temperature - reported as ln(D0) - of −4.71 ± 0.94 (2σ) m2/s. These values imply a bulk closure temperature for 4He in Durango fluorapatite of 74 °C for a 50 μm radius grain, infinite cylinder geometry, and a cooling rate of 10 °C/Myr. 相似文献
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Determination of Salinity in Fluid Inclusions with Laser Raman Spectroscopy Technique 总被引：2，自引：0，他引：2
Seyed Javad Moghaddasi 《中国地质大学学报(英文版)》2000,11(4)
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