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  • 1
    Online Resource
    Online Resource
    Carbon Nanotube–Multilayered Graphene Edge Plane Core–Shell Hybrid Foams for Ultrahigh‐Performance Electromagnetic‐Interference Shielding
    Wiley ; 2017
    In:  Advanced Materials Vol. 29, No. 31 ( 2017-08)
    Details
    In: Advanced Materials, Wiley, Vol. 29, No. 31 ( 2017-08)
    Abstract: Materials with an ultralow density and ultrahigh electromagnetic‐interference (EMI)‐shielding performance are highly desirable in fields of aerospace, portable electronics, and so on. Theoretical work predicts that 3D carbon nanotube (CNT)/graphene hybrids are one of the most promising lightweight EMI shielding materials, owing to their unique nanostructures and extraordinary electronic properties. Herein, for the first time, a lightweight, flexible, and conductive CNT–multilayered graphene edge plane (MLGEP) core–shell hybrid foam is fabricated using chemical vapor deposition. MLGEPs are seamlessly grown on the CNTs, and the hybrid foam exhibits excellent EMI shielding effectiveness which exceeds 38.4 or 47.5 dB in X‐band at 1.6 mm, while the density is merely 0.0058 or 0.0089 g cm −3 , respectively, which far surpasses the best values of reported carbon‐based composite materials. The grafted MLGEPs on CNTs can obviously enhance the penetration losses of microwaves in foams, leading to a greatly improved EMI shielding performance. In addition, the CNT–MLGEP hybrids also exhibit a great potential as nano‐reinforcements for fabricating high‐strength polymer‐based composites. The results provide an alternative approach to fully explore the potentials of CNT and graphene, for developing advanced multifunctional materials.
    Type of Medium: Online Resource
    ISSN: 0935-9648 , 1521-4095
    URL: Issue
    URL: Article
    DOI: 10.1002/adma.v29.31
    DOI: 10.1002/adma.201701583
    RVK:
    UA 1538
    Language: English
    Publisher: Wiley
    Publication Date: 2017
    detail.hit.zdb_id: 1474949-X
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  • 2
    Online Resource
    Online Resource
    Guiding Principles for Designing Highly Efficient Metal‐Free Carbon Catalysts
    Wiley ; 2019
    In:  Advanced Materials Vol. 31, No. 13 ( 2019-03)
    Details
    In: Advanced Materials, Wiley, Vol. 31, No. 13 ( 2019-03)
    Abstract: Carbon nanomaterials are promising metal‐free catalysts for energy conversion and storage, but the catalysts are usually developed via traditional trial‐and‐error methods. To rationally design and accelerate the search for the highly efficient catalysts, it is necessary to establish design principles for the carbon‐based catalysts. Here, theoretical analysis and material design of metal‐free carbon nanomaterials as efficient photo‐/electrocatalysts to facilitate the critical chemical reactions in clean and sustainable energy technologies are reviewed. These reactions include the oxygen reduction reaction in fuel cells, the oxygen evolution reaction in metal–air batteries, the iodine reduction reaction in dye‐sensitized solar cells, the hydrogen evolution reaction in water splitting, and the carbon dioxide reduction in artificial photosynthesis. Basic catalytic principles, computationally guided design approaches and intrinsic descriptors, catalytic material design strategies, and future directions are discussed for the rational design and synthesis of highly efficient carbon‐based catalysts for clean energy technologies.
    Type of Medium: Online Resource
    ISSN: 0935-9648 , 1521-4095
    URL: Issue
    URL: Article
    DOI: 10.1002/adma.v31.13
    DOI: 10.1002/adma.201805252
    RVK:
    UA 1538
    Language: English
    Publisher: Wiley
    Publication Date: 2019
    detail.hit.zdb_id: 1474949-X
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  • 3
    Online Resource
    Online Resource
    2D isotropic elastic Gaussian-beam migration for common-shot multicomponent records
    Society of Exploration Geophysicists ; 2018
    In:  GEOPHYSICS Vol. 83, No. 2 ( 2018-03-01), p. S127-S140
    Details
    In: GEOPHYSICS, Society of Exploration Geophysicists, Vol. 83, No. 2 ( 2018-03-01), p. S127-S140
    Abstract: Gaussian-beam migration (GBM) is flexible and adaptable for imaging geologically complicated areas. It avoids some limitations, such as amplitude singularity in caustic zones and an inability to image multiple arrivals, of traditional ray-based migration approaches. Previous studies on GBM mainly focused on acoustic media. We have developed a 2D isotropic elastic GBM scheme for common-shot multicomponent records. Our method extrapolates P- and S-mode wavefields simultaneously using the Kirchhoff-Helmholtz integral solution of the isotropic elastodynamic equation. We separate the extrapolated wavefields into compressional and shear modes using the Helmholtz decomposition, and we then implement a modified dot-product imaging condition. This approach enables us to produce clear PP-images and avoid polarity reversal issues for PS-images. In addition, based on the theory of wavefield approximation in the effective vicinity of central rays, we derive a formula to compute the propagation angles of paraxial rays, which can be used to extract angle-domain common-image gathers.
    Type of Medium: Online Resource
    ISSN: 0016-8033 , 1942-2156
    URL: Article
    DOI: 10.1190/geo2017-0078.1
    RVK:
    UA 4068.4
    Language: English
    Publisher: Society of Exploration Geophysicists
    Publication Date: 2018
    detail.hit.zdb_id: 2033021-2
    detail.hit.zdb_id: 2184-2
    SSG: 16,13
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  • 4
    Online Resource
    Online Resource
    A Bayesian approach to estimate uncertainty for full-waveform inversion using a priori information from depth migration
    Society of Exploration Geophysicists ; 2016
    In:  GEOPHYSICS Vol. 81, No. 5 ( 2016-09), p. R307-R323
    Details
    In: GEOPHYSICS, Society of Exploration Geophysicists, Vol. 81, No. 5 ( 2016-09), p. R307-R323
    Abstract: Full-waveform inversion (FWI) enables us to obtain high-resolution subsurface images; however, estimating model uncertainties associated with this technique is still a challenging problem. We have used a Bayesian inference framework to estimate model uncertainties associated with FWI. The uncertainties were assessed based on an a posteriori covariance operator, evaluated at the maximum a posteriori model. For the prior distribution, we have used a spatially nonstationary covariance operator based on a plane-wave construction with local dips measured from migrated images. Preconditioned frequency-domain FWI was used to estimate the maximum a posteriori model. Efficient manipulation of the posterior covariance was based on a low-rank approximation of the data misfit Hessian preconditioned by the prior covariance operator. The strong decay of the singular values indicated that data were mostly informative about a low-dimensional subspace of model parameters. To reduce computational cost of the randomized singular value decomposition, we have used a Hessian approximation based on point-spread functions. The 2D numerical examples with synthetic data confirmed that the method can effectively estimate uncertainties for FWI. Visual comparisons of random samples drawn from the prior and posterior distributions have allowed us to evaluate model uncertainties. Furthermore, we found out how statistical quantities, such as means and pointwise standard deviation fields, can be efficiently extracted from the prior and posterior distributions. These fields helped us to objectively assess subsurface images provided by FWI.
    Type of Medium: Online Resource
    ISSN: 0016-8033 , 1942-2156
    URL: Article
    DOI: 10.1190/geo2015-0641.1
    RVK:
    UA 4068.4
    Language: English
    Publisher: Society of Exploration Geophysicists
    Publication Date: 2016
    detail.hit.zdb_id: 2033021-2
    detail.hit.zdb_id: 2184-2
    SSG: 16,13
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  • 5
    Online Resource
    Online Resource
    A NEWTON-MULTIGRID METHOD FOR NUMERICAL SIMULATION OF SLIDER AIR BEARING
    World Scientific Pub Co Pte Ltd ; 2005
    In:  Modern Physics Letters B Vol. 19, No. 28n29 ( 2005-12-20), p. 1647-1650
    Details
    In: Modern Physics Letters B, World Scientific Pub Co Pte Ltd, Vol. 19, No. 28n29 ( 2005-12-20), p. 1647-1650
    Abstract: In this paper, a Newton-Multigrid method is presented to solve the numerical simulation of the slider air bearing. For each fixed attitude in the specified grid, the Newton method is used to achieve the pressure distribution of the slider by solving the generalized Reynolds equations discretized by the least square finite difference (LSFD) method. Between the different sizes of grids, full approximation multigrid method is used to accelerate the convergence rate by eliminating the dominating low frequency error mode in the late stages of convergence. From the case study of the slider air bearing, it shows that the Newton-Multigrid method is accurate and efficient for the numerical simulation problem.
    Type of Medium: Online Resource
    ISSN: 0217-9849 , 1793-6640
    URL: Article
    DOI: 10.1142/S0217984905010128
    RVK:
    UA 5534.B
    Language: English
    Publisher: World Scientific Pub Co Pte Ltd
    Publication Date: 2005
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  • 6
    Online Resource
    Online Resource
    Viscoacoustic reverse time migration with a robust space-wavenumber domain attenuation compensation operator
    Society of Exploration Geophysicists ; 2021
    In:  GEOPHYSICS Vol. 86, No. 5 ( 2021-09-01), p. S339-S353
    Details
    In: GEOPHYSICS, Society of Exploration Geophysicists, Vol. 86, No. 5 ( 2021-09-01), p. S339-S353
    Abstract: Intrinsic attenuation gives rise to phase dispersion and amplitude loss during seismic wave propagation. Not correcting these effects in seismic imaging can result in inaccurate reflector locations, dimmed amplitudes, and degraded spatial resolution. In reverse time migration (RTM), attenuation compensation can be implemented by reversing the sign of the dissipation term and keeping the dispersion term unchanged for backward wavefield extrapolation. Although this Q-compensated RTM scheme can effectively correct attenuation effects, amplitude amplification during backpropagation might lead to numerical instabilities, especially for field data with strong high-frequency noise. To mitigate this problem, we have developed a robust space-wavenumber compensation operator and applied it to viscoacoustic RTM. By analyzing the dispersion-only and viscoacoustic Green’s functions, we obtain an analytical solution for the attenuation compensation operator in a homogeneous medium. Because it is a time-frequency operator, to apply it directly in viscoacoustic RTM requires access to the extrapolated wavefields within a certain time window. To avoid storing the wavefields and improve the computational efficiency, we use an approximated dispersion relation and convert the time-frequency operator to an equivalent space-wavenumber operator, which allows us to implement attenuation compensation on the fly during wavefield extrapolation. The hybrid-domain property of the operator enables us to account for the wavenumber-dependent compensation. A similar strategy also can be applied to the migrated images as a poststack processing approach, which is more efficient than the prestack compensation. Two synthetic and one land field data set examples demonstrate the feasibility and adaptability of our method.
    Type of Medium: Online Resource
    ISSN: 0016-8033 , 1942-2156
    URL: Article
    DOI: 10.1190/geo2020-0608.1
    RVK:
    UA 4068.4
    Language: English
    Publisher: Society of Exploration Geophysicists
    Publication Date: 2021
    detail.hit.zdb_id: 2033021-2
    detail.hit.zdb_id: 2184-2
    SSG: 16,13
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  • 7
    Online Resource
    Online Resource
    A finite-difference approach for solving pure quasi-P-wave equations in transversely isotropic and orthorhombic media
    Society of Exploration Geophysicists ; 2018
    In:  GEOPHYSICS Vol. 83, No. 4 ( 2018-07-01), p. C161-C172
    Details
    In: GEOPHYSICS, Society of Exploration Geophysicists, Vol. 83, No. 4 ( 2018-07-01), p. C161-C172
    Abstract: Starting from the dispersion relation and setting S-wave velocity along symmetry axes to zero, pseudoacoustic-wave equations have been proposed to describe the kinematics of acoustic wavefields in transversely isotropic (TI) and orthorhombic media. To date, the numerical stability of the pseudoacoustic-wave equations has been improved by developing coupled systems of wave equations; however, most simulations still suffer from S-wave artifacts that are the fundamental solutions of the fourth- and sixth-order partial differential equations. Pure quasi-P-wave equations accurately describe the traveltimes of P-waves in TI and orthorhombic media and are free of S-wave artifacts. However, it is difficult to directly solve the pure quasi-P-wave equations using conventional finite-difference schemes due to the presence of pseudo-differential operators. We approximated these pseudo-differential operators by algebraic expressions, whose coefficients can be determined by minimizing differences between the true and approximated values of the pseudo-differential operators in the wavenumber domain. The derived new coupled systems involve modified acoustic-wave equations and a Poisson’s equation that can be solved by conventional finite-difference stencils and fast Poisson’s solver. Several 2D and 3D numerical examples demonstrate that the simulations based on the new systems are free of S-wave artifacts and have correct kinematics of quasi-P-waves in TI and orthorhombic media.
    Type of Medium: Online Resource
    ISSN: 0016-8033 , 1942-2156
    URL: Article
    DOI: 10.1190/geo2017-0405.1
    RVK:
    UA 4068.4
    Language: English
    Publisher: Society of Exploration Geophysicists
    Publication Date: 2018
    detail.hit.zdb_id: 2033021-2
    detail.hit.zdb_id: 2184-2
    SSG: 16,13
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  • 8
    Online Resource
    Online Resource
    Iron-doped VSe2 nanosheets for enhanced hydrogen evolution reaction
    AIP Publishing ; 2020
    In:  Applied Physics Letters Vol. 116, No. 22 ( 2020-06-01)
    Details
    In: Applied Physics Letters, AIP Publishing, Vol. 116, No. 22 ( 2020-06-01)
    Abstract: Alloying is critical for regulating the electron states of layered two-dimensional (2D) materials, which has a significant influence on the physical and chemical properties of 2D materials, such as electrochemical catalysis, magnetism, and the bandgap of semiconductors. Here, we report the alloy of Fe-doped VSe2 with good homogeneity at the atomic level by using a one-step synthesis method. Fe-doped VSe2 presents enhanced hydrogen evolution reaction (HER) performance. It is found that Fe-doped VSe2 shows improved catalytic activity compared to the virgin VSe2, including a lower overpotential and a smaller Tafel slope. The enhanced HER performance indicates a lower Gibbs free energy of the HER process, resulting from the doping-induced regulation of the electron states. Our work presents a facile method to prepare transition metal-doped 2D materials and offers a general way to regulate the catalytic properties of 2D materials for energy conversion applications.
    Type of Medium: Online Resource
    ISSN: 0003-6951 , 1077-3118
    URL: Article
    DOI: 10.1063/5.0008092
    RVK:
    UA 1000
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2020
    detail.hit.zdb_id: 211245-0
    detail.hit.zdb_id: 1469436-0
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