激光导线系统测定拱坝位移     

杨仁  潘正风 《武汉大学学报(信息科学版)》1988,(3)

根据生产实际的需要,本文提出一种激光导线系统,可用它来测定拱坝或其它曲线型建筑物的位移。本文对该系统的原理,转角棱镜的设计原则,棱镜安置误差对测定转析角变化量的精度影响,以及该系统的观测方法,拱坝位移量的计算等作了详细的论述。  相似文献   

三行线阵扫描数据的平差方案及精度分析   总被引：2，自引：0，他引：2  

张森林 《武汉大学学报(信息科学版)》1988,(4)

本文对平行排列的三行线性阵列扫描仪获取的数据,按不同的平差方案做了大量实验和理论分析,找到了平差系统不定解条件和使平差系统有最佳几何状态的参数选择方案。  相似文献   

用精密水准对激光准直垂直方向施加改正的探讨     

潘正风  花向红 《武汉大学学报(信息科学版)》1990,(1)

本文给出了激光准直系统垂直折光改正的数学模型。在温度梯度的精确值难以获得时,利用精密水准成果计算折光系数是行之有效的办法,文中还以BEPC工程为例,讨论了模型的具体应用。  相似文献   

非定值角光学倍增干涉测角方法     

仲思东 《武汉大学学报(信息科学版)》1990,(3)

本文提出了以非定值角倍增法进行小角度干涉测量的方法,推导出了非定值角激光干涉测角公式及有关的理论公式。依照该方法拟定了以光、机、电、算为核心的激光干涉小角度测量方案,并建立了一整套包括小角度旋转平台、测量干涉条纹宽度的光栅测量系统以及用微型计算机自动处理测量结果的小角度激光干涉测量装置。最后证明了理论结果与实验数据是相符合的,其测角可重复性误差小于0.″03。  相似文献   

Methane emissions from a landfill measured by eddy correlation using a fast response diode laser sensor     

D. C. Hovde  A. C. Stanton  T. P. Meyers  D. R. Matt 《Journal of Atmospheric Chemistry》1995,20(2):141-162

We describe a fast response methane sensor based on the absorption of radiation generated with a near-infrared InGaAsP diode laser. The sensor uses an open path absorption region 0.5 m long; multiple pass optics provide an optical path of 50 m. High frequency wavelength modulation methods give stable signals with detection sensitivity (S/N=1, 1 Hz bandwidth) for methane of 65 ppb at atmospheric pressure and room temperature. Improvements in the optical stability are expected to lower the current detection limit. We used the new sensor to measure, by eddy correlation, the CH₄ flux from a clay-capped sanitary landfill. Simultaneously we measured the flux of CO₂ and H₂O. From seven half-hourly periods of data collected after a rainstorm on November 23, 1991, the average flux of CH₄ was 17 mmol m^–2 hr^–1 (6400 mg CH₄ m^–2 d^–1) with a coefficient of variation of 25%. This measurement may underrepresent the flux by 15% due to roll-off of the sensor response at high frequency. The landfill was also a source of CO₂ with an average flux of 8.1 mmol m^–2 hr^–1 (8550 mg CO₂ m^–2 d^–1) and a coefficient of variation of 26%. A spectral analysis of the data collected from the CH₄, CO₂, and H₂O sensors showed a strong similarity in the turbulent transfer mechanisms.  相似文献   

SHRIMP U-Pb zircon dating from Sulu-Dabie dolomitic marble, eastern China: constraints on prograde, ultrahigh-pressure and retrograde metamorphic ages   总被引：15，自引：0，他引：15  

F. L. LIU  A. GERDES  J.G. LIOU  H. M. XUE  F. H. LIANG 《Journal of Metamorphic Geology》2006,24(7):569-589

Laser Raman spectroscopy and cathodoluminescence (CL) images show that zircon from Sulu‐Dabie dolomitic marbles is characterized by distinctive domains of inherited (detrital), prograde, ultrahigh‐pressure (UHP) and retrograde metamorphic growths. The inherited zircon domains are dark‐luminescent in CL images and contain mineral inclusions of Qtz + Cal + Ap. The prograde metamorphic domains are white‐luminescent in CL images and preserve a quartz eclogite facies assemblage of Qtz + Dol + Grt + Omp + Phe + Ap, formed at 542–693 °C and 1.8–2.1 GPa. In contrast, the UHP metamorphic domains are grey‐luminescent in CL images, retain the UHP assemblage of Coe + Grt + Omp + Arg + Mgs + Ap, and record UHP conditions of 739–866 °C and >5.5 GPa. The outermost retrograde rims have dark‐luminescent CL images, and contain low‐P minerals such as calcite, related to the regional amphibolite facies retrogression. Laser ablation ICP‐MS trace‐element data show striking difference between the inherited cores of mostly magmatic origin and zircon domains grown in response to prograde, UHP and retrograde metamorphism. SHRIMP U‐Pb dating on these zoned zircon identified four discrete ²⁰⁶Pb/²³⁸U age groups: 1823–503 Ma is recorded in the inherited (detrital) zircon derived from various Proterozoic protoliths, the prograde domains record the quartz eclogite facies metamorphism at 254–239 Ma, the UHP growth domains occurred at 238–230 Ma, and the late amphibolite facies retrogressive overprint in the outermost rims was restricted to 218–206 Ma. Thus, Proterozoic continental materials of the Yangtze craton were subducted to 55–60 km depth during the Early Triassic and recrystallized at quartz eclogite facies conditions. Then these metamorphic rocks were further subducted to depths of 165–175 km in the Middle Triassic and experienced UHP metamorphism, and finally these UHP metamorphic rocks were exhumed to mid‐crustal levels (about 30 km) in the Late Triassic and overprinted by regional amphibolite facies metamorphism. The subduction and exhumation rates deduced from the SHRIMP data and metamorphic P–T conditions are 9–10 km Myr^?1 and 6.4 km Myr^?1, respectively, and these rapid subduction–exhumation rates may explain the obtained P–T–t path. Such a fast exhumation suggests that Sulu‐Dabie UHP rocks that returned towards crustal depths were driven by buoyant forces, caused as a consequence of slab breakoff at mantle depth.  相似文献   

Trace Element Analysis of Fused Whole-Rock Glasses by Laser Ablation-ICP-MS and PIXE     

Masanori Kurosawa  Kunihiro Shima  Satoshi Ishii  Kimikazu Sasa 《Geostandards and Geoanalytical Research》2006,30(1):17-30

The concentrations of fifty trace elements, including relatively volatile elements and transition metal elements, in fused glasses of Geological Survey of Japan rock reference materials GSJ JR-2, JA-1, JA-2, JB-1a, JB-3, JGb-1 and JF-1 were determined by particle (proton) induced X-ray emission (PIXE) and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). The fused glasses were prepared by rapid fusion and subsequent quenching in welded platinum capsules and were found to be homogeneous for major elements and for trace elements with concentrations of more than 1 μg g^-1 within the observed precision (± 10% mean) on a 70 μm sampling scale. The values obtained by PIXE and LA-ICP-MS for the transition elements (Cr, Mn, Fe, Ni and Cu), the relatively volatile elements (Zn, Ga, Rb and Pb) and the refractory elements (Y, Zr, Nb and Th) with concentrations greater than a few μg g^-1 showed good agreement (within 10 % relative difference). The values for almost all the elements detected at concentrations higher than 1 μg g^-1 as determined by LA-ICP-MS also agreed well with the reference values (mean relative difference < ± 10%), except for B and Cu. The good agreement confirmed the appropriateness of the NIST SRM 600 series glass calibration reference material for LA-ICP-MS analysis of glasses with variable major-element compositions for almost all elements. The concentrations of Cu in all the samples were lower than the reference values, which was attributed to adsorption of the transition metals onto the platinum capsule during preparation.  相似文献   

Trends in Analytical Developments and Earth Science Applications in LA-ICP-MS and LA-MC-ICP-MS for 2004 and 2005   总被引：1，自引：0，他引：1  

Paul J. Sylvester 《Geostandards and Geoanalytical Research》2006,30(3):197-207

This review of laser ablation-inductively coupled plasma-mass spectrometry includes research that employed quadrupole instruments, and single-collector and multicollector magnetic sector field instruments. The most important trend in 2004–2005 was the growing appreciation that small matrix effects in LA-(MC)-ICP-MS need to be addressed in order to produce highly precise and accurate data by the method. The issue is most acute for isotope ratio measurements that require standard-sample-standard bracketing but can also be important for certain elemental analysis. Matrix-dependent elemental and isotopic fractionations were studied from the standpoint of laser-sample interactions and the behaviour of laser-generated particles in the ablation cell, transfer tubing and ICP torch. Innovations in LA-(MC)-ICP-MS involved signal smoothing, in torch laser ablation, on-line isotope dilution and molecular oxide monitoring. Other important research was carried out on the calibration and homogeneity of various reference materials; and the exploration of mature ( in situ U-Pb geochronology) and emerging (apatite fission-track chronometry, U-Th/He thermochronology, boron/strontium/uranium-series isotopic microanalysis) applications in the Earth sciences.  相似文献   

我国进行激光测月的研究   总被引：1，自引：0，他引：1  

魏二虎  常亮  刘经南 《测绘信息与工程》2006,31(3):1-3

概述了全球激光测月的现状,分析了其困难和改进方法及我国开展激光测月的意义,提出了对我国开展激光测月工作的建议。  相似文献   

Local accuracy measures for digital terrain models   总被引：1，自引：0，他引：1  

Karl  Kraus  Wilfried  Karel  Christian  Briese  Gottfried  Mandlburger 《The Photogrammetric Record》2006,21(116):342-354

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