铁同位素分析测试技术研究进展   总被引：5，自引：3，他引：2  

秦燕  徐衍明  侯可军  李延河  陈蕾 《岩矿测试》2020,39(2):151-161

铁是地球上丰度最高的变价元素,在自然界大量分布于各类矿物、岩石、流体和生物体中,并广泛参与成岩作用、成矿作用、热液活动和生命活动过程。铁同位素组成对地球化学、天体化学和生物化学方面提供重要的信息,是同位素地球化学研究领域的热点。铁同位素的精确测量是开展相关研究的重要基础。本文评述了铁同位素测试技术的研究进展,主要包括:①溶液法测试铁同位素样品纯化过程中阴离子树脂的改进;②质谱分析从传统的热电离质谱法发展为多接收电感耦合等离子体质谱法;③激光微区原位测试技术的研发等。在此基础上,对测试过程中会导致产生铁同位素分馏的步骤和校正方法进行了总结,并对各种测试方法的优缺点进行了评述。本文认为:溶液法分析流程长且复杂,但分析精度高(0.03‰,2SD)、方法稳定;微区原位分析方法从纳秒激光剥蚀发展为飞秒激光剥蚀,脉冲持续时间更短、脉冲峰值强度更高(可达10~(12)W),聚焦强度超过10~(20)W/cm~2,使其具有分析速度快、空间分辨率高的优势。微区原位法可以从微观角度去讨论铁同位素变化的地球化学过程,但基体效应的存在限制了微区原位铁同位素的广泛应用。因此,缩短溶液法分析流程,开发系列基体匹配的标准样品,是铁同位素分析方法研发的方向。  相似文献   

High‐Precision,High‐Accuracy Oxygen Isotope Measurements of Zircon Reference Materials with the SHRIMP‐SI     

Janaína N. vila  Trevor R. Ireland  Peter Holden  Peter Lanc  Andrew Latimore  Norm Schram  John Foster  Ian S. Williams  Liane Loiselle  Bin Fu 《Geostandards and Geoanalytical Research》2020,44(1):85-102

Analytical protocols for SHRIMP‐SI oxygen isotope analysis (δ¹⁸O) of a suite of zircon reference materials (RMs) are presented. Data reduction involved a robust estimate of uncertainties associated with the individual spot as well as for groups where the spot data are combined. The repeatability of δ¹⁸O measurements is dependent on both the analytical conditions and the choice of the primary reference material. Under optimised conditions, repeatability was often better than 0.4‰ (2s) allowing sample uncertainties to be obtained to better than 0.2‰ (at 95% confidence limit). Single spot uncertainty combined the within‐spot precision with the scatter associated with repeated measurements of the primary zircon reference material during a measurement session. The uncertainty for individual spots measured under optimised conditions was between 0.3 and 0.4‰ (at 95% confidence). The analytical protocols described were used to assess a variety of zircon RMs that have been used for geochronology and for which laser fluorination oxygen isotope data are available (Temora 2, FC1, R33, QGNG and Ple?ovice), as well as zircons that have been used as RMs for trace element or other types of determination (Mud Tank, Monastery, 91500, AS57, AS3, KIM‐5, OG1, SL13, CZ3 and several other Sri Lankan zircons). Repeated analyses over nine sessions and seven different mounts show agreement within analytical uncertainty for Temora 2, FC1, R33, QGNG, Ple?ovice and 91500, when normalised to Mud Tank. For existing ion microprobe mounts with these materials, an appropriate δ¹⁸O can be determined. However, care should be taken when using zircons from the Duluth Complex (i.e., FC1, AS57 and AS3) as reference materials as our data indicated an excess scatter on δ¹⁸O values associated with low‐U zircon grains.  相似文献   

Identification of modal parameters of a 600-m-high skyscraper from field vibration tests     

Junwei Zhang  Qiusheng Li 《地震工程与结构动力学》2019,48(15):1678-1698

Accurate prediction of the dynamic responses of a high-rise building subjected to dynamic loads such as earthquake and wind excitations requires the information of its structural dynamic properties such as modal parameters including natural frequencies and damping ratios. This paper presents the identification results of the modal parameters based on field vibration tests on a 600-m high skyscraper. A set of tests, including ambient vibration test (AVT) and free vibration test (FVT), were conducted on the skyscraper to identify its modal parameters. Firstly, this paper presents and discusses the modal parameters of the skyscraper assessed by several identification methods applied to the AVT measurements. These methods include the wavelet transform (WT) method, the stochastic subspace identification (SSI) method, and the random decrement technique (RDT). Secondly, an active mass damper (AMD) system with total mass 1000 tons equipped into the skyscraper was used to excite the building for estimation of the modal parameters by FVT. Thirdly, this paper presents observations on the structural dynamic behavior of the skyscraper with the operation of the AMD system during a typhoon event. The field measurement results show that the AMD system functioned efficiently for suppression of the wind-induced vibrations of the skyscraper during the typhoon. This paper aims to further understand the structural dynamic properties of super-tall buildings and provide useful information for structural design and vibration control of future skyscrapers.  相似文献   

基于水资源约束的中国城镇化SD模型与模拟   总被引：1，自引：0，他引：1  

曹祺文  鲍超  顾朝林  管卫华 《地理研究》2019,38(1):167-180

中国城镇化正处于快速发展阶段,尽管经济和社会发展主控要素还在发挥重要作用,但水资源在生产、生活和生态方面发挥主控作用的局面愈益明显。在中国城镇化系统动力学（system dynamics,SD）模型基础上,从水资源供给、需求和水环境等层面将水资源作为主控要素嵌入原有模型中,拓展出基于水资源约束的中国城镇化SD模型,并对水资源利用进行了多情景模拟。结果表明：① 系统存流量和灵敏度检验证明模型模拟效果良好,具有可操作性。② 部门用水效率一定时,产业发展对水资源供需平衡的影响比人口增长更为明显。③ 在实行节水农业、节水工业、高生活需水、高生态环境需水和高再生水利用的综合协调方案中,2050年中国城镇化的发展约共需6789.70亿 m³水资源,基本实现水资源供需平衡。  相似文献   

An improved input energy spectrum verified by the shake table tests     

Ahmet Güllü  Ercan Yüksel  Cem Yalçın  A. Anıl Dindar  Hasan Özkaynak  Oral Büyüköztürk 《地震工程与结构动力学》2019,48(1):27-45

Input energy is the principal component of the energy balance equation. It is beneficial to determine, through its components, how the recoverable and irrecoverable energies are distributed within the structural elements. Several equations and attenuation relations to define mass-normalized input energy spectra exist in the literature. They are mainly proposed for elastic systems subjected to far-fault EQs. There is a lack of experimental verification of these proposed spectra. In this paper, experimental assessment was performed to the existing spectra, and further improvements were accomplished. For this purpose, steel cantilever columns were tested on the shake table for two specific historical EQs coincidently having similar spectral acceleration values. Based on the experimental results, a three-part mass-normalized relative input energy spectrum was formulated including soil type, EQ (corner period, intensity, duration, spectral acceleration, and velocity), and structural behavioral characteristics (period and structural damping). The proposed input energy spectrum was experimentally calibrated and numerically validated for various EQs featuring near- and far-field types. Analytical and experimental comparisons were made between the previously developed spectrum and the newly proposed one. The validation studies and the statistical evaluations exposed that the proposed spectrum yielded better agreement with the experimental and numerical results.  相似文献   

Strain analysis of a seismically imaged mass‐transport complex,offshore Uruguay     

Michael J. Steventon  Christopher A.‐L. Jackson  David M. Hodgson  Howard D. Johnson 《Basin Research》2019,31(3):600-620

Strain style, magnitude and distribution within mass‐transport complexes (MTCs) are important for understanding the process evolution of submarine mass flows and for estimating their runout distances. Structural restoration and quantification of strain in gravitationally driven passive margins have been shown to approximately balance between updip extensional and downdip contractional domains; such an exercise has not yet been attempted for MTCs. We here interpret and structurally restore a shallowly buried (c. 1,500 mbsf) and well‐imaged MTC, offshore Uruguay using a high‐resolution (12.5 m vertical and 15 × 12.5 m horizontal resolution) three‐dimensional seismic‐reflection survey. This allows us to characterise and quantify vertical and lateral strain distribution within the deposit. Detailed seismic mapping and attribute analysis shows that the MTC is characterised by a complicated array of kinematic indicators, which vary spatially in style and concentration. Seismic‐attribute extractions reveal several previously undocumented fabrics preserved in the MTC, including internal shearing in the form of sub‐orthogonal shear zones, and fold‐thrust systems within the basal shear zone beneath rafted‐blocks. These features suggest multiple transport directions and phases of flow during emplacement. The MTC is characterised by a broadly tripartite strain distribution, with extensional (e.g. normal faults), translational and contractional (e.g. folds and thrusts) domains, along with a radial frontally emergent zone. We also show how strain is preferentially concentrated around intra‐MTC rafted‐blocks due to their kinematic interactions with the underlying basal shear zone. Overall, and even when volume loss within the frontally emergent zone is included, a strain difference between extension (1.6–1.9 km) and contraction (6.7–7.3 km) is calculated. We attribute this to a combination of distributed, sub‐seismic, ‘cryptic’ strain, likely related to de‐watering, grain‐scale deformation and related changes in bulk sediment volume. This work has implications for assessing MTCs strain distribution and provides a practical approach for evaluating structural interpretations within such deposits.  相似文献   

Lifecycle cost optimization of tuned mass dampers for the seismic improvement of inelastic structures     

Emiliano Matta 《地震工程与结构动力学》2018,47(3):714-737

The seismic performance of tuned mass dampers (TMDs) on structures undergoing inelastic deformations may largely depend on the ground motion intensity. By estimating the impact of each seismic intensity on the overall cost of future seismic damages, lifecycle cost (LCC) proves a rational metric for evaluating the benefits of TMDs on inelastic structures. However, no incorporation of this metric into an optimization framework is reported yet. This paper presents a methodology for the LCC‐optimal design of TMDs on inelastic structures, which minimizes the total seismic LCC of the combined building‐TMD system. Its distinctive features are the assumption of a mass‐proportional TMD cost model, the adoption of an iterative suboptimization procedure, and the initialization of the TMD frequency and damping ratios according to a conventional linear TMD design technique. The methodology is applied to the seismic improvement of the SAC‐LA benchmark buildings, taken as representative of standard steel moment‐resisting frame office buildings in LA, California. Results show that, despite their limited performance at the highest intensity levels, LCC‐optimal TMDs considerably reduce the total LCC, to an extent that depends on both the building vulnerability and the TMD unit cost. They systematically present large mass ratios (around 10%) and frequency and damping ratios close to their respective linearly designed optima. Simulations reveal the effectiveness of the proposed design methodology and the importance of adopting a nonlinear model to correctly evaluate the cost‐effectiveness of TMDs on ordinary structures in highly seismic areas.  相似文献   

海洋气团对沿海城市大气环境影响与识别研究     

石红旗  王霄曈  张昊阳  石博欣  张睿 《海洋科学》2018,42(12):100-108

本研究通过识别海洋气团特征及沿海城市大气受到海洋气团的影响方式与程度,为评价沿海城市空气环境质量提供科学依据。以青岛市为例,收集大气气溶胶样品中放射性核素~(210)Pb、40K数据及采集时段当地大气颗粒物数据;分析~(210)Pb活度浓度与气溶胶颗粒物浓度变化;对当地当时大气气团进行溯源分析。研究表明:(1)研究期间青岛沿岸地区2015年4月至2016年6月与2016年6月至2017年6月大气污染特征显著不同,前者~(210)Pb活度浓度与污染颗粒物浓度显著相关,而后者~(210)Pb活度浓度与污染颗粒物无相关关系;(2)穿越海洋的陆地气团呈现出高活度浓度、低颗粒物浓度的特征;来自海洋气团的气溶胶呈现出低活度浓度、低颗粒物浓度的特征;(3)海洋气团气溶胶中~(210)Pb活度浓度较低。临近大陆的海洋(黄海、东海)上层大气受到大陆气团的影响,其海洋气团的特征有所减弱。~(210)Pb活度浓度、颗粒物浓度(PM2.5)可作为判断海洋气团的指标,识别"来自海洋的气团"与"经过海洋的气团"。  相似文献   

Comprehensive study of the drying behavior of Boom clay: Experimental investigation and numerical modeling          下载免费PDF全文

Julien Hubert  Erwan Plougonven  Noémie Prime  Angélique Léonard  Frédéric Collin 《国际地质力学数值与分析法杂志》2018,42(2):211-230

This paper presents a thermo‐hydro‐mechanical framework to model the drying behavior of Boom clay. First, the experimental campaign conducted Noémie Prime is briefly presented because it is used to validate the model. The data acquisition and processing is emphasized because of the use of X‐ray microtomography to be able to more accurately compare experimental and numerical strain fields. The different submodels are introduced. Numerical simulations are performed to illustrate the capability of the proposed model to reproduce the observed behavior. Finally, a comprehensive sensitivity study on several key model parameters associated with the water retention curve, and the permeability of the medium, is performed to get a better understanding of the physics behind the coupled model.  相似文献   

Artificial recharge efficiency assessment by soil water balance and modelling approaches in a multi-layered vadose zone in a dry region     

Mojtaba Pakparvar  Hossein Hashemi  Meisam Rezaei  Wim M. Cornelis  Gholamali Nekooeian  Sayyed Ahang Kowsar 《水文科学杂志》2018,63(8):1183-1202

To assess recharge through floodwater spreading, three wells, approx. 30 m deep, were dug in a 35-year-old basin in southern Iran. Hydraulic parameters of the layers were measured. One well was equipped with pre-calibrated time domain reflectometry (TDR) sensors. The soil moisture was measured continuously before and after events. Rainfall, ponding depth and the duration of the flooding events were also measured. Recharge was assessed by the soil water balance method, and by calibrated (inverse solution) HYDRUS-1D. The results show that the 15 wetting front was interrupted at a layer with fine soil accumulation over a coarse layer at the depth of approx. 4 m. This seemed to occur due to fingering flow. Estimation of recharge by the soil water balance and modelling approaches showed a downward water flux of 55 and 57% of impounded floodwater, respectively.  相似文献