نتایج جستجو برای: geochemical

تعداد نتایج: 12072  

Journal: :Journal of contaminant hydrology 2012
Gautham P Jeppu T Prabhakar Clement Mark O Barnett Kang-Kun Lee

It is difficult to design column experiments to study transport processes involving slow geochemical reactions that require long residence times to reach equilibrium. We propose a sequential equilibration reactor (SER) setup to study such equilibrium geochemical reactive transport problems. The proposed system consists of sequentially operated batch reactors that directly mimic typical one-dime...

2017
Kenneth G. Miller James D. Wright

We review examples of placement of select Cenozoic Global Boundary Stratotype Sections and Points (GSSP = “golden spikes”) from a geochemical and magnetostratigraphic perspective. Though biostratigraphy is the sine qua non for placing modern chronologic tools (high-resolution radiometric dates, magnetochronology, and astrochronology) into proper stratigraphic context, its use as the primary cor...

2012
tiMotej VerBoVŠek

Paper focuses on the analysis of geochemical data with values below the limit of detection (LOD). Such values are treated as text and are difficult to use in further calculations of mean, standard deviation and other statistical parameters. To estimate several methods for substitution of values below the LOD with fractions of LOD (zero, LOD/2, LOD/√2, LOD and no data values), a large dataset of...

2009
Marina V. FRONTASYEVA

Place and role of nuclear analytical techniques (NATs) in life sciences is discussed. Examples of radioanalytical investigations at the IBR-2 pulsed fast reactor in Dubna illustrate the environmental, biomedical, geochemical and industrial applications of instrumental neutron activation analysis.

Journal: :SIAM Journal of Applied Mathematics 2003
J. H. Stout Paul H. Edelman S. W. Peterson Victor Reiner

The problem of predicting the possible topologies of a geochemical phase diagram, based on the chemical formula of the phases involved, is shown to be intimately connected with and aided by well-studied notions in discrete geometry: Gale diagrams, triangulations, secondary fans, and oriented matroids.

Journal: :Philosophical transactions. Series A, Mathematical, physical, and engineering sciences 2013
Ivan L'Heureux

Chemical oscillating patterns are ubiquitous in geochemical systems. Although many such patterns result from systematic variations in the external environmental conditions, it is recognized that some patterns are due to intrinsic self-organized processes in a non-equilibrium nonlinear system with positive feedback. In rocks and minerals, periodic precipitation (Liesegang bands) and oscillatory ...

2007
Roger N. Anderson E. Dove

Estimates of elemental and mineralogical abundances from geochemical logs are compared to preliminary chemical and modal analyses from cores in the Cajon Pass Scientific Drillhole. Accuracies of log-computed weight percent oxide and mineralogy determinations range from 10 to 30%.

Identification of geochemical anomalies is a significant step during regional geochemical exploration. In this matter, new techniques have been developed based on deep learning networks. These simple-structure-networks act like our brains on processing the data by simulating deep layers of thinking. In this paper, a hybrid compositional-deep learning technique was applied to identify the anomal...

2001
B. A. Cohen

Introduction: The aim of this abstract is to acquaint the reader with the major geochemical and geochronological properties of lunar rocks formed or affected by impact events, and thus how these rocks constrain lunar bombardment history, with particular emphasis on constraints upon the proposed Lunar Cataclysm or Late Heavy Bombardment [1]. To this end, the focus is on clast-poor impact melt ro...

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