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221.
Michael Wiedenbeck Robert B. Trumbull Martin Rosner Adrian Boyce John H. Fournelle Ian A. Franchi Ralf Halama Chris Harris Jack H. Lacey Horst Marschall Anette Meixner Andreas Pack Philip A.E. Pogge von Strandmann Michael J. Spicuzza John W. Valley Franziska D.H. Wilke 《Geostandards and Geoanalytical Research》2021,45(1):97-119
Three tourmaline reference materials sourced from the Harvard Mineralogical and Geological Museum (schorl 112566, dravite 108796 and elbaite 98144), which are already widely used for the calibration of in situ boron isotope measurements, are characterised here for their oxygen and lithium isotope compositions. Homogeneity tests by secondary ion mass spectrometry (SIMS) showed that at sub‐nanogram test portion masses, their 18O/16O and 7Li/6Li isotope ratios are constant within ± 0.27‰ and ± 2.2‰ (1s), respectively. The lithium mass fractions of the three materials vary over three orders of magnitude. SIMS homogeneity tests showed variations in 7Li/28Si between 8% and 14% (1s), which provides a measure of the heterogeneity of the Li contents in these three materials. Here, we provide recommended values for δ18O, Δ’17O and δ7Li for the three Harvard tourmaline reference materials based on results from bulk mineral analyses from multiple, independent laboratories using laser‐ and stepwise fluorination gas mass spectrometry (for O), and solution multi‐collector inductively coupled plasma‐mass spectroscopy (for Li). These bulk data also allow us to assess the degree of inter‐laboratory bias that might be present in such data sets. This work also re‐evaluates the major element chemical composition of the materials by electron probe microanalysis and investigates these presence of a chemical matrix effect on SIMS instrumental mass fractionation with regard to δ18O determinations, which was found to be < 1.6‰ between these three materials. The final table presented here provides a summary of the isotope ratio values that we have determined for these three materials. Depending on their starting mass, either 128 or 512 splits have been produced of each material, assuring their availability for many years into the future. 相似文献
222.
Failure of nonstructural components during an earthquake can lead to structure functionality loss, cause widespread property damage, and pose a life-safety threat to the occupants. Current code provisions for floor-anchored components aim to minimize the life safety threat by specifying lateral force demands and anchoring requirements. These code requirements are based on a simplified equation that does not fully consider the contribution of the attachment to the overall component dynamic response. Previous results from shaking-table tests of anchored components suggest that the component attachment is an important parameter that determines its dynamic properties. For this study, a nonstructural experimental model was attached via several attachment designs to a concrete slab and tested on a shaking table to evaluate this contribution. The attachments were dimensioned based on a capacity design approach, such that they would be the weakest element in the force path while providing a yielding mechanism. The attachment designs provide different plastic mechanisms that control the displacement ductility in the response of the component. This paper focuses on the contribution of the attachment to the dynamic response and seismic force demand on the component. The experimental results demonstrate that the selected attachment properties govern the boundary conditions of the nonstructural component and strongly influence its dynamic response. The more flexible attachments sustained large deformations, leading to tensile membrane action and enhanced tensile strength in the attachments. Consequently, the ductile attachments did not result in reduced seismic loads in the nonstructural components. 相似文献
223.
Journal of Seismology - This project evaluates the existing statistical models to describe post-shut-in seismicity for hydraulic-fracturing-induced earthquakes and studies the importance of... 相似文献
224.
Quaternary climate change and Heinrich events in the southern Balkans: Lake Prespa diatom palaeolimnology from the last interglacial to present 总被引:1,自引:0,他引:1
225.
Su Yaling Li Kuanyi Zhang Yongdong Liu Zhengwen Wang Tijian Jeppesen Erik Middelburg Jack J. Smol John P. 《Journal of Paleolimnology》2022,68(3):249-263
Journal of Paleolimnology - Autochthonous and allochthonous organic carbon (OC) are important carbon sources for zooplankton in lakes, and changes in the abundance and proportions of those sources... 相似文献
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Jack Wen Wei Guo Ali Ashasi-Sorkhabi Oya Mercan Constantin Christopoulos 《地震工程与工程振动(英文版)》2017,16(4):693-711
A user-programmable computational/control platform was developed at the University of Toronto that offers real-time hybrid simulation (RTHS) capabilities. The platform was verified previously using several linear physical substructures. The study presented in this paper is focused on further validating the RTHS platform using a nonlinear viscoelastic-plastic damper that has displacement, frequency and temperature-dependent properties. The validation study includes damper component characterization tests, as well as RTHS of a series of single-degree-of-freedom (SDOF) systems equipped with viscoelastic-plastic dampers that represent different structural designs. From the component characterization tests, it was found that for a wide range of excitation frequencies and friction slip loads, the tracking errors are comparable to the errors in RTHS of linear spring systems. The hybrid SDOF results are compared to an independently validated thermalmechanical viscoelastic model to further validate the ability for the platform to test nonlinear systems. After the validation, as an application study, nonlinear SDOF hybrid tests were used to develop performance spectra to predict the response of structures equipped with damping systems that are more challenging to model analytically. The use of the experimental performance spectra is illustrated by comparing the predicted response to the hybrid test response of 2DOF systems equipped with viscoelastic-plastic dampers. 相似文献
229.
Charles J. Paradis Emma R. Dixon Lauren M. Lui Adam P. Arkin Jack C. Parker Jonathan D. Istok Edmund Perfect Larry D. McKay Terry C. Hazen 《Ground water》2019,57(2):292-302
The breakthrough curve obtained from a single-well push-pull test can be adjusted to account for dilution of the injection fluid in the aquifer fluid. The dilution-adjusted breakthrough curve can be analyzed to estimate the reaction rate of a solute. The conventional dilution-adjusted method assumes that the ratios of the concentrations of the nonreactive and reactive solutes in the injection fluid vs. the aquifer fluid are equal. If this assumption is invalid, the conventional method will generate inaccurate breakthrough curves and may lead to erroneous conclusions regarding the reactivity of a solute. In this study, a new method that generates a dilution-adjusted breakthrough curve was theoretically developed to account for any possible combination of nonreactive and reactive solute concentrations in the injection and aquifer fluids. The newly developed method was applied to a field-based data set and was shown to generate more accurate dilution-adjusted breakthrough curves. The improved dilution-adjusted method presented here is simple, makes no assumptions regarding the concentrations of the nonreactive and reactive solutes in the injection and aquifer fluids, and easily allows for estimating reaction rates during push-pull tests. 相似文献
230.
Jack Dangermond 《地球空间信息科学学报》2020,23(1):1-9
ABSTRACTMany visions for geospatial technology have been advanced over the past half century. Initially researchers saw the handling of geospatial data as the major problem to be overcome. The vision of geographic information systems arose as an early international consensus. Later visions included spatial data infrastructure, Digital Earth, and a nervous system for the planet. With accelerating advances in information technology, a new vision is needed that reflects today’s focus on open and multimodal access, sharing, engagement, the Web, Big Data, artificial intelligence, and data science. We elaborate on the concept of geospatial infrastructure, and argue that it is essential if geospatial technology is to contribute to the solution of problems facing humanity. 相似文献