The Experts below are selected from a list of 183 Experts worldwide ranked by ideXlab platform
Eric Kirby - One of the best experts on this subject based on the ideXlab platform.
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late cenozoic evolution of the eastern margin of the tibetan plateau inferences from 40ar 39ar and u th he thermochronology
Tectonics, 2002Co-Authors: Peter W Reiners, Michael A Krol, Kelin X Whipple, K V Hodges, Kenneth A. Farley, Eric Kirby, W. Tang, Zhiliang ChenAbstract:High topography in central Asia is perhaps the most Fundamental Expression of the Cenozoic Indo-Asian collision, yet an understanding of the timing and rates of development of the Tibetan Plateau remains elusive. Here we investigate the Cenozoic thermal histories of rocks along the eastern margin of the plateau adjacent to the Sichuan Basin in an effort to determine when the steep topographic escarpment that characterizes this margin developed. Temperature-time paths inferred from ^(40)Ar/^(39)Ar thermochronology of biotite, multiple diffusion domain modeling of alkali feldspar ^(40)Ar release spectra, and (U-Th)/He thermochronology of zircon and apatite imply that rocks at the present-day topographic front of the plateau underwent slow cooling ( 30°–50°C/m.y.) coincident with exhumation from inferred depths of ∼8–10 km, at denudation rates of 1–2 mm/yr. Samples from the interior of the plateau continued to cool relatively slowly during the same time period (∼3°C/m.y.), suggesting limited exhumation (1–2 km). However, these samples record a slight increase in cooling rate (from <1 to ∼3°C/m.y.) at some time during the middle Tertiary; the tectonic significance of this change remains uncertain. Regardless, late Cenozoic denudation in this region appears to have been markedly heterogeneous, with the highest rates of exhumation focused at the topographic front of the plateau margin. We infer that the onset of rapid cooling at the plateau margin reflects the erosional response to the development of regionally significant topographic gradients between the plateau and the stable Sichuan Basin and thus marks the onset of deformation related to the development of the Tibetan Plateau in this region. The present margin of the plateau adjacent to and north of the Sichuan Basin is apparently no older than the late Miocene or early Pliocene (∼5–12 Ma).
Zhiliang Chen - One of the best experts on this subject based on the ideXlab platform.
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late cenozoic evolution of the eastern margin of the tibetan plateau inferences from 40ar 39ar and u th he thermochronology
Tectonics, 2002Co-Authors: Peter W Reiners, Michael A Krol, Kelin X Whipple, K V Hodges, Kenneth A. Farley, Eric Kirby, W. Tang, Zhiliang ChenAbstract:High topography in central Asia is perhaps the most Fundamental Expression of the Cenozoic Indo-Asian collision, yet an understanding of the timing and rates of development of the Tibetan Plateau remains elusive. Here we investigate the Cenozoic thermal histories of rocks along the eastern margin of the plateau adjacent to the Sichuan Basin in an effort to determine when the steep topographic escarpment that characterizes this margin developed. Temperature-time paths inferred from ^(40)Ar/^(39)Ar thermochronology of biotite, multiple diffusion domain modeling of alkali feldspar ^(40)Ar release spectra, and (U-Th)/He thermochronology of zircon and apatite imply that rocks at the present-day topographic front of the plateau underwent slow cooling ( 30°–50°C/m.y.) coincident with exhumation from inferred depths of ∼8–10 km, at denudation rates of 1–2 mm/yr. Samples from the interior of the plateau continued to cool relatively slowly during the same time period (∼3°C/m.y.), suggesting limited exhumation (1–2 km). However, these samples record a slight increase in cooling rate (from <1 to ∼3°C/m.y.) at some time during the middle Tertiary; the tectonic significance of this change remains uncertain. Regardless, late Cenozoic denudation in this region appears to have been markedly heterogeneous, with the highest rates of exhumation focused at the topographic front of the plateau margin. We infer that the onset of rapid cooling at the plateau margin reflects the erosional response to the development of regionally significant topographic gradients between the plateau and the stable Sichuan Basin and thus marks the onset of deformation related to the development of the Tibetan Plateau in this region. The present margin of the plateau adjacent to and north of the Sichuan Basin is apparently no older than the late Miocene or early Pliocene (∼5–12 Ma).
Peter W Reiners - One of the best experts on this subject based on the ideXlab platform.
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late cenozoic evolution of the eastern margin of the tibetan plateau inferences from 40ar 39ar and u th he thermochronology
Tectonics, 2002Co-Authors: Peter W Reiners, Michael A Krol, Kelin X Whipple, K V Hodges, Kenneth A. Farley, Eric Kirby, W. Tang, Zhiliang ChenAbstract:High topography in central Asia is perhaps the most Fundamental Expression of the Cenozoic Indo-Asian collision, yet an understanding of the timing and rates of development of the Tibetan Plateau remains elusive. Here we investigate the Cenozoic thermal histories of rocks along the eastern margin of the plateau adjacent to the Sichuan Basin in an effort to determine when the steep topographic escarpment that characterizes this margin developed. Temperature-time paths inferred from ^(40)Ar/^(39)Ar thermochronology of biotite, multiple diffusion domain modeling of alkali feldspar ^(40)Ar release spectra, and (U-Th)/He thermochronology of zircon and apatite imply that rocks at the present-day topographic front of the plateau underwent slow cooling ( 30°–50°C/m.y.) coincident with exhumation from inferred depths of ∼8–10 km, at denudation rates of 1–2 mm/yr. Samples from the interior of the plateau continued to cool relatively slowly during the same time period (∼3°C/m.y.), suggesting limited exhumation (1–2 km). However, these samples record a slight increase in cooling rate (from <1 to ∼3°C/m.y.) at some time during the middle Tertiary; the tectonic significance of this change remains uncertain. Regardless, late Cenozoic denudation in this region appears to have been markedly heterogeneous, with the highest rates of exhumation focused at the topographic front of the plateau margin. We infer that the onset of rapid cooling at the plateau margin reflects the erosional response to the development of regionally significant topographic gradients between the plateau and the stable Sichuan Basin and thus marks the onset of deformation related to the development of the Tibetan Plateau in this region. The present margin of the plateau adjacent to and north of the Sichuan Basin is apparently no older than the late Miocene or early Pliocene (∼5–12 Ma).
Blaise Ravelo - One of the best experts on this subject based on the ideXlab platform.
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High-Pass Negative Group Delay RC-Network Impedance
IEEE Transactions on Circuits and Systems II: Express Briefs, 2017Co-Authors: Blaise RaveloAbstract:This brief describes a synthesis of high-pass negative group delay (NGD) network impedance. The Fundamental Expression of the high-pass NGD canonical transfer function is established. Based on the circuit impedance equivalent principle, the high-pass NGD first-order network that is constituted by RC lumped elements is identified. The identified topology basic NGD characteristics are formulated and analyzed. Then, the associated synthesis method in function of the desired NGD optimal level and cutoff frequency is established. The theory is validated by design, simulations, and measurements of proof-of-concept prototypes. A good agreement between the theoretical prediction and experimental results showing high-pass NGD response from 1 MHz with minimal level of about -10 ns is observed. The high-pass NGD function operates at high frequencies with first-order circuit.
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Design of ‗|‗ Shape Stub Based Negative Group Delay Circuit
IEEE Design & Test, 1Co-Authors: Ningdong Li, Blaise Ravelo, Wenceslas Rahajandraibe, Sébastien LalléchèreAbstract:This paper deals with a design method of negative group delay (NGD) circuit built with a completely new topology consisted of distributed reverse T-shape stub. The microwave passive topology is originally constituted by totally distributed circuit built with reverse T-stub mounted in parallel. The NGD topology stub is composed of two identical coupled-lines (CLs) and three identical transmission lines (TLs). An innovative modelling approach based on the combination of ABCD- and Z-matrices is developed in order to model the two-port equivalent S-parameter. The equivalent schematic analysis enables to establish the Fundamental Expression of the reverse T-stub input impedance by considering the interbranch coupling effect. Then, the group delay (GD) is expressed in function of the CL coupling coefficient and the stub branch element physical lengths. Then, the NGD analysis confirms the possibility to generate NGD with the reverse T-stub topology under study. The NGD existence condition in function of the CL parameters is formulated. The relevance of the reverse T-stub NGD theory is approved with a microstrip circuit proof-of-concept. An NGD level of approximately -1 ns was simulated and measured around the center frequency 1.89 GHz. The fabricated reverse T-stub NGD prototype presents an insertion loss better than 2 dB and reflection loss better than 15 dB in the NGD bandwidth.
V. V. Zagorodny - One of the best experts on this subject based on the ideXlab platform.
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X-Ray Fluorescence Analysis of Nonhomogeneous Materials by Δμ-Correction Method
Advances in x-ray analysis, 1991Co-Authors: V. I. Karmanov, V. V. ZagorodnyAbstract:AbstractThe Fundamental parameters method (FPM) enables one to determine with high accuracy the chemical composition of homogeneous samples, having only one reference sample. However, the reference sample composition should be similar to that of the samples analyzed.The x-ray fluorescence analysis of multicomponent heterogeneous materials (ores, minerals, their mixtures, welding electrode coating mixtures, fluxes, etc.) is made by the Δμ-correction method based on the combined use of the Fundamental and empirical correlations maintaining all the advantages of the FPM. Sample composition is calculated on the basis of the element intensities measured in the sample and in the reference specimen and is corrected for the disturbing effect of excitation conditions and heterogeneity as well as the calculated values of one of the Fundamental parameters (μ1). At the preliminary stage of calibration, the coefficients are determined using regression and the absolute Fundamental Expression for the element fluorescence intensity.
