The Experts below are selected from a list of 4143 Experts worldwide ranked by ideXlab platform
Alain Tabbagh - One of the best experts on this subject based on the ideXlab platform.
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Quantifying multiple electromagnetic properties in EMI surveys: A case study of hydromorphic soils in a volcanic context – The Lac du Puy (France)
Geoderma, 2020Co-Authors: François Xavier Simon, Mathias Pareilh-peyrou, Solène Buvat, Alfredo Mayoral, Philippe Labazuy, Karim Kelfoun, Alain TabbaghAbstract:We used two different loop-loop electromagnetic induction (EMI) devices to determine the 3D geometry and morphology of the pedo-sedimentary filling and underlying basaltic bedrock of a former wetland in a volcanic soil area, the Lac du Puy depression (Auvergne, France). Electrical conductivity (or resistivity) is usually sufficient for environmental and soil science applications, but the local volcanic context of the survey area results in high values of magnetic susceptibility and possible electrical polarization effects. Therefore we investigated the roles of the four properties: electrical conductivity, magnetic susceptibility, magnetic viscosity and dielectric permittivity. We created models using these four properties for the two coil configurations of each device in order to assess the degree to which each of the properties contributed to the recorded electromagnetic signal. The results show that electrical conductivity controls the Quadrature Component of the secondary field response but that it can be affected by high values of magnetic viscosity, while magnetic susceptibility controls the in-phase Component. Moreover, the low frequencies imply a limited contribution of dielectric permittivity to the in-phase Component, except in the cases of higher permittivity or frequency values or greater inter-coil separation. Based on these observations, we propose a way to map the apparent properties from field measurements. We then carried out a 1D inversion, first by considering the electrical conductivity alone and secondly by taking all the electromagnetic properties into account. The results show that there is a marked contrast in the complex magnetic susceptibility between the sedimentary in-fill and the border of the Lac de Puy depression, (stronger than for the electrical conductivity), and that permittivity is unlikely to have a significant influence. The shape and nature of the sedimentary in-fill was thus considerably refined by the second inversion results based on the three other properties. These data, combined with litho-stratigraphic observations from a previous study, allowed the lateral continuity and geometry of the in-fill to be assessed across the whole basin. Results are also consistent with previous interpretations of the depression as a pseudo-sinkhole, a relatively common morphology in volcanic plateaus. Analysis of the magnetic properties also made it possible to characterize the spatial variation of some key features related to hydromorphic processes, such as clayey granularity and the development of iron oxides/hydroxides. This opens up the possibility for using new methods for rapid spatial and pedological characterization of hydromorphic soils and palaeosoils.
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Complex Susceptibility Measurement Using Multi-frequency Slingram EMI Instrument
2014Co-Authors: François Xavier Simon, Alain Tabbagh, Julien Thiesson, J.c. Donati, A. SarrisAbstract:Complex magnetic susceptibility is a well-known property both theoretically and experimentally. To achieve this measurement, different ways have been tested, like TDEM or multi-frequential measurement on soil sample. In this study we carry out the measurements by the use of a multi-frequential EMI Slingram instrument to collect data quickly and in-situ. The use of multi-frequency data is also a way to correct effects of the conductivity on the in-phase Component and effects of the magnetic susceptibility on the Quadrature Component of the raw signal.
Ehsan Afshari - One of the best experts on this subject based on the ideXlab platform.
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A CMOS Noise-Squeezing Amplifier
IEEE Transactions on Microwave Theory and Techniques, 2012Co-Authors: Wooram Lee, Ehsan AfshariAbstract:Noise squeezing occurs through phase-sensitive gain implemented by a parametric process in a nonlinear LC resonator. This process enhances the sensitivity for one Quadrature Component of an input signal at the expense of degrading the sensitivity for the other Quadrature. We demonstrate an 8.75-GHz parametric resonant amplifier in a 0.13-μm CMOS process, which provides gain of 21 dB and 12 dB for the two Quadrature Components. This 9-dB gain difference results in a 2.5-dB sensitivity improvement for one Quadrature, while it degrades the other Quadrature sensitivity by 6.4 dB. The amplifier bandwidth is around 800 MHz and draws 36 mA from a 1.2-V supply.
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Low-Noise Parametric Resonant Amplifier
IEEE Transactions on Circuits and Systems I: Regular Papers, 2011Co-Authors: Wooram Lee, Ehsan AfshariAbstract:We propose a resonant parametric amplifier with an enhanced noise performance by exploiting the noise-squeezing effect. Noise squeezing occurs through the phase-sensitive amplification process and suppresses one of the two Quadrature Components of the input noise. When the input signal is only in the direction of the nonsuppressed Quadrature Component, squeezing can lower that noise figure by almost 3 dB. The resonant structure of the proposed amplifier is inspired by a Fabry-Perot laser amplifier to achieve the squeezing effect using a low number of LC elements. We design and simulate the proposed noise-squeezing parametric amplifier in a conventional 65-nm CMOS process. A minimum noise-squeezing factor of -0.35 dB is achieved with a signal gain of 26 dB for one Quadrature Component of a 10-GHz narrow-band signal.
Van De Vijver, Ellen - One of the best experts on this subject based on the ideXlab platform.
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Offset errors in probabilistic inversion of small-loop frequency-domain electromagnetic data: a synthetic study on their influence on magnetic susceptibility estimation
'Society of Exploration Geophysicists', 2019Co-Authors: Bobe Christin, Van De Vijver, EllenAbstract:Small-loop frequency-domain electromagnetic (FDEM) devices measure a secondary magnetic field caused by the application of a stronger primary magnetic field. Both the in-phase and Quadrature Component of the secondary field commonly suffer from systematic measurement errors, which would result in a non-zero response in free space. The in-phase response is typically strongly correlated to subsurface magnetic susceptibility. Considering common applications on weakly to moderately susceptible grounds, the in-phase Component of the secondary field is usually weaker than the Quadrature Component, making it relatively more prone to systematic errors. Incorporating coil-specific offset parameters in a probabilistic inversion framework, we show how systematic errors in FDEM measurements can be estimated jointly with electrical conductivity and magnetic susceptibility. Including FDEM measurements from more than one height, the offset estimate becomes closer to the true offset, allowing an improved inversion result for the subsurface magnetic susceptibility.Comment: Conference: Workshop on Gravity, Electrical and Magnetic Methods and Their Application
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Offset errors in probabilistic inversion of small-loop frequency-domain electromagnetic data : a synthetic study on their influence on magnetic susceptibility estimation
'Society of Exploration Geophysicists', 2019Co-Authors: Bobe Christin, Van De Vijver, EllenAbstract:Small-loop frequency-domain electromagnetic (FDEM) devices measure a secondary magnetic field caused by the application of a stronger primary magnetic field. Both the in-phase and Quadrature Component of the secondary field commonly suffer from systematic measurement errors, which would result in a non-zero response in free space. The in-phase response is typically strongly correlated to subsurface magnetic susceptibility. Considering common applications on weakly to moderately susceptible grounds, the in-phase Component of the secondary field is usually weaker than the Quadrature Component, making it relatively more prone to systematic errors. Incorporating coil-specific offset parameters in a probabilistic inversion framework, we show how systematic errors in FDEM measurements can be estimated jointly with electrical conductivity and magnetic susceptibility. Including FDEM measurements from more than one height, the offset estimate becomes closer to the true offset, allowing an improved inversion result for the subsurface magnetic susceptibility
Akira Furusawa - One of the best experts on this subject based on the ideXlab platform.
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Quantum nondemolition measurement of a light field Component by a feedback compensated beam splitter
arXiv: Quantum Physics, 2001Co-Authors: Holger F. Hofmann, Takayoshi Kobayashi, Akira FurusawaAbstract:In conventional quantum nondemolition measurements, the interaction between signal and probe preserves the measured variable. Alternatively, it is possible to restore the original value of the variable by feedback. In this paper, we describe a quantum nondemolition measurement of a Quadrature Component of the light field using a feedback compensated beam splitter. The noise induced by the vacuum port of the beam splitter is compensated by a linear feedback resulting in an effective amplification of the observed variable. This amplification is then be reversed by optical parametric amplification to restore the original value of the field Component.
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Nonclassical correlations of photon number and field Components in the vacuum state
Physical Review A, 2000Co-Authors: Holger F. Hofmann, Takayoshi Kobayashi, Akira FurusawaAbstract:It is shown that the quantum jumps in the photon number n from zero to one or more photons induced by backaction evasion quantum nondemolition measurements of a Quadrature Component x of the vacuum light field state are strongly correlated with the Quadrature Component measurement results. This correlation corresponds to the operator expectation value which is equal to one fourth for the vacuum even though the photon number eigenvalue is zero. Quantum nondemolition measurements of a Quadrature Component can thus provide experimental evidence of the nonclassical operator ordering dependence of the correlations between photon number and field Components in the vacuum state.
D G Welsch - One of the best experts on this subject based on the ideXlab platform.
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generating schrodinger cat like states by means of conditional measurements on a beam splitter
Physical Review A, 1997Co-Authors: M Dakna, T Anhut, Tomas Opatrný, L Knoll, D G WelschAbstract:A scheme for generating Schrodinger-cat-like states of a single-mode optical field by means of conditional measurement is proposed. Feeding a squeezed vacuum into a beam splitter and counting the photons in one of the output channels, the conditional states in the other output channel exhibit a number of properties that are very similar to those of superpositions of two coherent states with opposite phases. We present analytical and numerical results for the photon-number and Quadrature-Component distributions of the conditional states and their Wigner and Husimi functions. Further, we discuss the effect of realistic photocounting on the states. @S1050-2947~97!06404-4#
