New sedimentological and palynological data from the Yarkand-Fergana Basin(Kyrgyz Tian Shan): Insights on its Mesozoic paleogeographic and tectonic evolution     

Julien Morin  Marc Jolivet  Dave Shaw  Sylvie Bourquin  Elena Bataleva 《地学前缘(英文版)》2021,12(1):183-202

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Compositional variability on the surface of 4 Vesta revealed through GRaND measurements of high‐energy gamma rays     

Patrick N. Peplowski  David J. Lawrence  Thomas H. Prettyman  Naoyuki Yamashita  Dave Bazell  William C. Feldman  Lucille Le Corre  Timothy J. McCoy  Vishnu Reddy  Robert C. Reedy  Chris T. Russell  Michael J. Toplis 《Meteoritics & planetary science》2013,48(11):2252-2270

Measurements of the high‐energy gamma‐ray flux emanating from asteroid 4 Vesta by the Dawn Gamma‐Ray and Neutron Detector (GRaND) have revealed variability in the near‐surface elemental composition of the Vestan surface. These observations are consistent with the presence of large (≥8 × 10⁴ km²) regions with distinct, HED‐like elemental compositions. The results agree broadly with other global measurements, such as the macroscopic neutron absorption cross section and spectral reflectance‐derived mineralogic maps. Two distinct regions with eucrite‐like elemental compositions have been identified, the first located primarily within the Lucaria and Marcia quadrangles and the second within Oppia quadrangle. The former region is collocated with some of the oldest, most heavily cratered terrain on Vesta. The interior of the 500 km diameter Rheasilvia impact basin is found to have a composition that is consistent with diogenite‐like material. Taken together, these observations support the hypothesis that Vesta's original crust was composed of basaltic outflows in the form of eucritic‐like material and that the Rheasilvia‐basin‐forming impact exposed lower‐crustal, diogenite‐like material. These measurements also constrain the maximum amount of mesosiderite‐like material to <10% for each 15 × 15° surface element.  相似文献   

Gauging the impact of fishing mortality on non-target species   总被引：4，自引：4，他引：0  

Pope  John G.; Macdonald  Dave S.; Daan  Niels; Reynolds  John D.; Jennings  Simon 《ICES Journal of Marine Science》2000,57(3):689-696

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基于深度学习卷积神经网络的地震波形自动分类与识别   总被引：9，自引：0，他引：9       下载免费PDF全文

赵明  陈石  Dave Yuen 《地球物理学报》2019,62(1):374-382

发展高效、高精度、普适性强的自动波形拾取算法在地震大数据时代背景下显得越来越重要.波形自动拾取算法的主要挑战来自如何适应不同区域的不同类型地震事件的分类与筛选.本文针对地震事件-噪音分类这一问题,使用13839个汶川地震余震事件建立数据集,应用深度学习卷积神经网络(CNN)方法进行训练,并用8900个新的汶川余震事件作为检测数据集,其训练和检测准确率均达到95%以上.在对连续波形的检测中,CNN方法在精度和召回率上优于STA/LTA和Fbpicker传统方法,并能找出大量人工挑选极易遗漏的微震事件.最后,我们应用训练好的最优模型对选自全国台网的441个台站8天的连续波形数据进行了识别、到时挑取及与参考地震目录关联,CNN检出7016段波形,用自动挑选算法拾取到1380对P,S到时,并与540个地震目录事件成功关联,对1级以上事件总体识别准确率为54%,二级以上为80%,证明了CNN模型具有泛化能力,初步展示了CNN在发展兼具效率、精度、普适性算法,实时地震监测等应用上具有巨大潜力.  相似文献   

Performance Assessment of Pump‐and‐Treat Systems          下载免费PDF全文

Michael Truex  Chris Johnson  Tamzen Macbeth  Dave Becker  Kira Lynch  Dominic Giaudrone  Aaron Frantz    Hope Lee 《Ground Water Monitoring & Remediation》2017,37(3):28-44

Pump‐and‐treat (P&T) is a widely applied remedy for groundwater remediation at many types of sites for multiple types of contaminants. Decisions regarding major changes in the remediation approach are an important element of environmental remediation management for a site using P&T. While existing guidance documents provide information on design, operation, and optimization for P&T systems, these documents do not provide specific technical guidance to support remedy decisions regarding when to transition to a new remedy or to initiate closure of the P&T remedy. A structured approach for P&T performance assessment was developed and is described herein, using analysis of three example P&T systems. These examples highlight key aspects of the performance assessment decision logic and represent assessment outcomes associated with optimizing the P&T system, transitioning from P&T to natural attenuation, and supplementing P&T with another technology to hasten transition to natural attenuation.  相似文献   

Potential Impacts to Groundwater from Ground‐Coupled Geothermal Heat Pumps in District Scale   总被引：1，自引：0，他引：1       下载免费PDF全文

Lee J. Florea  Dave Hart  James Tinjum  Chris Choi 《Ground water》2017,55(1):8-9

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Clastic injectites,internal structures and flow regime during injection: The Sea Lion Injectite System,North Falkland Basin     

Thomas J. H. Dodd  Dave J. McCarthy  Stuart M. Clarke 《Sedimentology》2020,67(2):1014-1044

This paper details and describes a suite of 143 sub-seismic-scale clastic injectites encountered within the early Cretaceous, early post-rift of the deep-lacustrine North Falkland Basin. The injectites, referred to here as the Sea Lion Injectite System, are encountered below, above and in between the hydrocarbon-bearing, deep-lacustrine turbidite sandstones of the Bleaker 30, Sea Lion North, Sea Lion, Casper and Beverley fans. Sedimentary structures are documented within the injectites including: planar laminations, mud-clast imbrication and clast alignment. Clasts align along centimetre-scale foresets formed through ripple-scale bedform migration in a hydraulically-open fracture. The style of flow within the injectite system is interpreted as initially through fluid turbulence during an open fracture phase, which was followed by a later stage where laminar flow dominated, most likely during the closing phase of the fracture system. The host rocks display evidence for ductile deformation, which along with ptygmatic folding of dykes and internally injected mud-clasts, suggests a period of injection into relatively uncompacted sediments. Evidence for brittle fracturing, in the form of stepped margins may be indicative of a separate phase of emplacement into more-compacted sediments. This variability in deformation styles is related to multi-phased injection episodes into host strata at different stages of consolidation and lithification at shallow burial depths. Injectites have been identified in four stratigraphic groupings: above the Bleaker 30 Fan and within/above the Sea Lion North Fan; within the hydrocarbon-bearing Sea Lion Fan; overlying the Sea Lion Fan; and above/below the hydrocarbon-bearing Casper and Beverley fans. This spatial association with the hydrocarbon-bearing fans of the North Falkland Basin is important, considering the ability of injectite networks to form effective fluid-flow conduits in the subsurface. Consequently, the findings of this study will improve the characterization of sub-seismic scale injectites (and therefore fluid conduits) within otherwise impermeable strata.  相似文献   

Dynamic response characterization and simplified analysis methods for viscoelastic dampers considering heat transfer     

Kazuhiko Kasai  Dave Montellano Osabel  Daiki Sato 《地震工程与结构动力学》2023,52(1):27-50

Viscoelastic (VE) dampers are sensitive to temperature, excitation frequency, and strain level. As they dissipate the kinetic energy from earthquake or wind-induced structural vibrations, their temperature increases from the heat generated, consequently softening their VE materials and lowering their dynamic mechanical properties. Temperature increase can be significant for long-duration loading, but can be limited by heat conduction and convection which depend on damper configuration. The writers analytically explored such effect on the six different dampers by using their previously proposed three-dimensional finite-element analysis method. Results provided better understanding of how heat is generated within the VE material, conducted and stored in different damper parts, and dispersed to the surrounding air. These results also led to characterization of both local (e.g., temperatures, properties, and strain energy density) and global (e.g., hysteresis loops, and stiffness) behavior of VE dampers, and provided a framework for a new simplified one-dimensional (1D) modeling approach for time-history analysis. This new proposed 1D method greatly improves the computation time of the previously proposed long-duration method coupling fractional time-derivatives VE constitutive rule with 1D heat transfer analysis. Unlike the previous method, it idealizes uniform shear strain and VE material property distributions for computational efficiency, but still simulating non-uniform temperature distribution along the thickness direction of the VE material. Despite the approximations, it accurately predicts VE damper global responses.  相似文献