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Lin Zhu Ren-Xu Chen Yong-Fei Zheng Jing Wang Bing Gong 《Geostandards and Geoanalytical Research》2023,47(1):105-124
An accurate determination of water content in garnet is critical to quantify the transport of water to the deep mantle by the subducted oceanic crust beyond the breakdown of hydrous phases. Fourier transform infrared spectroscopy (FTIR) is the most widely used approach to determine the species and contents of water in garnet. Accurate quantification of OH in garnet requires independent calibration using an external method, as OH absorbance is mineral and composition specific. To obtain the infrared absorption coefficients of structural hydroxyl in garnet, a combined study of spectrometric analyses by FTIR and a method combining a thermal conversion elemental analyser with isotope ratio mass spectrometry (TC/EA-MS) was carried out for fourteen gem-quality natural garnet crystals with variable compositions. The obtained molar absorption coefficients were 9322 ± 338 and 240 ± 26 l mol−1 cm−2 for grossular- and spessartine-rich garnet and pyrope-almandine garnet, respectively. These results are within the range of previous studies. A new molar absorption coefficient of 689 ± 177 l mol−1 cm−2 was obtained for pyrope-spessartine garnet. The large variation in the absorption coefficient indicates it is controlled by both garnet composition and OH-absorption bands. The obtained absorption coefficients are only appropriate for certain types of eclogitic garnet, and more studies should be carried out on eclogitic garnets. 相似文献
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便携式消费级无人机相机标定有效性评估 总被引:1,自引:0,他引:1
本文针对近年来在各行业中广泛使用的便携式消费级无人机开展了相机标定有效性研究,分别通过室内标定场和后处理软件对相机进行标定和自标定,在对比无相机标定、飞前相机标定、飞后相机标定和自标定迭代校正等方法所得成图精度后,对不同相机标定方案的有效性进行了评估。结果表明:各种方案成图总体精度差别不大;飞前、飞后相机标定与无相机标定的成图精度相当;自标定迭代校正的成图精度略高于其他方案。可见采用航拍照片自标定参数迭代校正的方法更适合于飞行控制精度和成像系统稳定性都不高的便携式消费级无人机相机标定。 相似文献
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随着航空摄影测量及倾斜摄影技术的不断推广,其相机传感器受内在及外在因素的影响,使得相机畸变参数的准确性并不是稳定如一,因而极大限制了数据处理的效率。针对这一问题,本文以解决相机畸变参数的准确性作为出发点,从相机成像原理出发,分析相机成像中的误差,介绍相机标定的方法,对相机标定进行实验分析,以达到准确标定相机参数的目的,并将计算的畸变参数应用于实际项目的空中三角测量。试验结果表明,获取的畸变参数可提高空三的效率及稳定性。 相似文献
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本文利用误差分布和概率统计分析改进了波速比计算方法.对于震源位置相对集中的震群活动,对台站震相到时进行两次差分,通过对差分后的震相数据对进行二维高斯分布拟合,可以稳健地估计震群活动震源区波速比.该方法充分利用了不同台站Pg、Sg到时差的所有信息,其优势是不需要地震事件的震源位置,并且不依赖震源区以外的速度变化,有效消除了震源区到台站的传播路径效应的影响;相对于传统的平均波速比,本文方法得到的震源区波速比,更能真实地反映震源区介质的性质.我们将该方法应用到2013—2016年的乳山震群,结果显示:震源区波速比的变化与震群活动过程密切相关,波速比的变化反映了序列活动的阶段性特征. 相似文献
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The formation of subsurface freshwater lenses on top of brackish groundwater is a fascinating hydrologic phenomenon that creates groundwater supplies of great potential value in arid regions. Information on the recharge quantity and mechanism of these lenses is both scarce and uncertain. This study examines the formation and macroscale stability of the Rawdatain freshwater lens in Kuwait, for which significant pre-development data are available. The Rawdatain is a large (150 million m3) subsurface freshwater lens overlying brackish groundwater compared to the other freshwater lenses in the Arabian Peninsula. In this study, a three-dimensional (3D) density-dependent groundwater flow model is tested against the following data targets to estimate long-term diffuse and focused groundwater recharge: (i) groundwater head, (ii) total dissolved solids (TDS) groundwater concentration, (iii) volume and vertical thickness of stored groundwater of three different water quality TDS ranges (0–700, 700–1000 and 1000–2000 mg/L) and (iv) geometrical shape features of the lens along cross-sections. To better represent the spatial variation in TDS, six different recharge zones were assigned to allocate diffuse and focused recharge conditions. Twelve recharge rate scenarios, encompassing a wide range of feasible long-term average annual recharge values (200,000–5,000,000 m3/year), were tested against the multiple targets and compared with the groundwater age of the Rawdatain lens. Based on comparison with data targets, the long-term average annual recharge is estimated to be 500,000 m3/year. Scenarios of reduced recharge, which may occur due to changes in land-use or climate, demonstrate the extremely slow response of the lens, which is in agreement with the slow development and formation of the lens (>2,000 years). Within a 100-year time frame, a 50% reduction in annual recharge reduces the lens volumes by 21, 17 and 9% for the three water quality categories, respectively. This study demonstrates the stability of freshwater lenses in arid regions and also provides methodology for similar focused rainfall recharge freshwater lenses. 相似文献
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Developing,choosing and using landscape evolution models to inform field‐based landscape reconstruction studies 下载免费PDF全文
A.J.A.M. Temme J. Armitage M. Attal Wouter van Gorp T.J. Coulthard J.M. Schoorl 《地球表面变化过程与地形》2017,42(13):2167-2183
Landscape evolution models (LEMs) are an increasingly popular resource for geomorphologists as they can operate as virtual laboratories where the implications of hypotheses about processes over human to geological timescales can be visualized at spatial scales from catchments to mountain ranges. Hypothetical studies for idealized landscapes have dominated, although model testing in real landscapes has also been undertaken. So far however, numerical landscape evolution models have rarely been used to aid field‐based reconstructions of the geomorphic evolution of actual landscapes. To help make this use more common, we review numerical landscape evolution models from the point of view of model use in field reconstruction studies. We first give a broad overview of the main assumptions and choices made in many LEMs to help prospective users select models appropriate to their field situation. We then summarize for various timescales which data are typically available and which models are appropriate. Finally, we provide guidance on how to set up a model study as a function of available data and the type of research question. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
30.
针对当前地震微测井仪器在施工和数据采集方面的难题,从提高数据采集质量及仪器功能性方面提出了几种改进方法.主要利用MEMS加速度传感器结合多路并行处理采集方法设计了数字检波器,并集成姿态检测技术直接实现水平分量数据的校正功能,保证系统采集的质量;提出了Ethernet-RS485分布式总线自动控制技术,实现各级联探管的随机组合,同时采用电动方式控制探管操作,提高系统的集成化程度.文中详细分析了利用姿态检测技术实现水平分量数据校正的方法,解决了级联探管随机组合控制和震源激发方位的判定问题.仪器单节探管支持三分量并行采集,有效分辨率达18位,参数可远程配置,同时具备快速显示探管姿态的功能,且支持远程控制,非常适于复杂环境下的工程勘探,整个系统实现全数字化操作且仅需四芯电缆互连,从而缩小了设备的体积和重量,降低施工布线的复杂性. 相似文献