Single-pixel imaging of a translational object

Image-free tracking methods based on single-pixel detectors (SPDs) can track a moving object at a very high frame rate, but they rarely can achieve simultaneous imaging of such an object. In this study, we propose a method for simultaneously obtaining the relative displacements and images of a translational object. Four binary Fourier patterns and two differential Hadamard patterns are used to modulate one frame of the object and then modulated light signals are obtained by SPD. The relative displacements and image of the moving object can be gradually obtained along with the detection. The proposed method does not require any prior knowledge of the object and its motion. The method has been verified by simulations and experiments, achieving a frame rate of 3332 Hz to acquire relative displacements of a translational object at a spatial resolution of $128 \times 128$ pixels using a 20000-Hz digital micro-mirror device. This proposed method can broaden the application of image-free tracking methods and obtain spatial information about moving objects.Comment: 15 pages, 9 figures, 1 tabl

Tracking and fast imaging of a translational object via Fourier modulation

The tracking and imaging of high-speed moving objects hold significant promise for application in various fields. Single-pixel imaging enables the progressive capture of a fast-moving translational object through motion compensation. However, achieving a balance between a short reconstruction time and a good image quality is challenging. In this study, we present a approach that simultaneously incorporates position encoding and spatial information encoding through the Fourier patterns. The utilization of Fourier patterns with specific spatial frequencies ensures robust and accurate object localization. By exploiting the properties of the Fourier transform, our method achieves a remarkable reduction in time complexity and memory consumption while significantly enhancing image quality. Furthermore, we introduce an optimized sampling strategy specifically tailored for small moving objects, significantly reducing the required dwell time for imaging. The proposed method provides a practical solution for the real-time tracking, imaging and edge detection of translational objects, underscoring its considerable potential for diverse applications.Comment: 6 figure

Mechanisms of reservoir pore/throat characteristics evolution during long-term waterflooding

Formation pore structure and reservoir parameters change continually during waterflooding due to sand production, clay erosion, and pressure/temperature variation, which causes great challenge in geological modeling and simulation. In this work, the XA Oilfield, a block with more than 20 years’ waterflooding history, is used as an example to better understand the fundamental evolution mechanisms of reservoir pore network characteristics over long time waterflooding. We performed a large number of core analyses and experiments to obtain formation parameters (e.g., permeability, porosity, relative permeability, and etc.) at different development stages. The comparison illustrates that reservoir permeability can not only decrease with clay plugging, but also increase by the detachment of fine particles and even the destruction of microscopic structure. We also observed that the point/line contacts among grains decreases, the pore network connectivity increases, the clay content reduces and the rock trends to be more hydrophilic with increasing water injection. Moreover, we developed a pore network model to simulate the variation of formation parameter. The model parameters are also compared and analyzed to get a qualitative understanding of the evolvement laws, which will provide a useful guidance for reservoir accurate modeling.Cited as: Wang, S., Han, X., Dong, Y., et al. Mechanisms of reservoir pore/throat characteristics evolution during long-term waterflooding. Advances in Geo-Energy Research, 2017, 1(3): 148-157, doi: 10.26804/ager.2017.03.0

Observation of fourfold Dirac nodal line semimetal and its unconventional surface responses in sonic crystals

Three-dimensional nodal line semimetals (NLSMs) provide remarkable importance for both enrich topological physics and wave management. However, NLSMs realized in acoustic systems are twofold bands degenerate, which are called Weyl NLSMs. Here, we first report on the experimental observation of novel Dirac NLSMs with fourfold degenerate in sonic crystals. We reveal that the topological properties of the Dirac NLSMs are entirely different than that of the conventional Weyl NLSMs. The Berry phase related to the Dirac nodal line (DNL) is 2{\pi}, which results in the surface responses of the Dirac NLSMs with two radically different situations: a torus surface state occupying the entire surface Brillouin zone (SBZ) and without any surface state in the SBZ. We further reveal that topological surface arcs caused by DNL can change from open to closed contours. The findings of Dirac NLSMs and their unique surface response may provoke exciting frontiers for flexible manipulation of acoustic surface waves.Comment: 6 pages, 4 figure

Recent progress in 2D group-VA semiconductors: from theory to experiment

This review provides recent theoretical and experimental progress in the fundamental properties, electronic modulations, fabrications and applications of 2D group-VA materials.</p

Intralayer Negative Poisson's Ratio in Two-Dimensional Black Arsenic by Strain Engineering

Negative Poisson's ratio as the anomalous characteristic generally exists in artificial architectures, such as re-entrant and honeycomb structures. The structures with negative Poisson's ratio have attracted intensive attention due to their unique auxetic effect and many promising applications in shear resistant and energy absorption fields. However, experimental observation of negative Poisson's ratio in natural materials barely happened, although various two-dimensional layered materials are predicted in theory. Herein, we report the anisotropic Raman response and the intrinsic intralayer negative Poisson's ratio of two-dimensional natural black arsenic (b-As) via strain engineering strategy. The results were evident by the detailed Raman spectrum of b-As under uniaxial strain together with density functional theory calculations. It is found that b-As was softer along the armchair than zigzag direction. The anisotropic mechanical features and van der Waals interactions play essential roles in strain-dependent Raman shifts and negative Poisson's ratio in the natural b-As along zigzag direction. This work may shed a light on the mechanical properties and potential applications of two-dimensional puckered materials.Comment: 23 pages, 4 figure

Possible Luttinger liquid behavior of edge transport in monolayer transition metal dichalcogenide crystals.

In atomically-thin two-dimensional (2D) semiconductors, the nonuniformity in current flow due to its edge states may alter and even dictate the charge transport properties of the entire device. However, the influence of the edge states on electrical transport in 2D materials has not been sufficiently explored to date. Here, we systematically quantify the edge state contribution to electrical transport in monolayer MoS2/WSe2 field-effect transistors, revealing that the charge transport at low temperature is dominated by the edge conduction with the nonlinear behavior. The metallic edge states are revealed by scanning probe microscopy, scanning Kelvin probe force microscopy and first-principle calculations. Further analyses demonstrate that the edge-state dominated nonlinear transport shows a universal power-law scaling relationship with both temperature and bias voltage, which can be well explained by the 1D Luttinger liquid theory. These findings demonstrate the Luttinger liquid behavior in 2D materials and offer important insights into designing 2D electronics

Silicon Layer Intercalation of Centimeter-Scale, Epitaxially-Grown Monolayer Graphene on Ru(0001)

We develop a strategy for graphene growth on Ru(0001) followed by silicon-layer intercalation that not only weakens the interaction of graphene with the metal substrate but also retains its superlative properties. This G/Si/Ru architecture, produced by silicon-layer intercalation approach (SIA), was characterized by scanning tunneling microscopy/spectroscopy and angle resolved electron photoemission spectroscopy. These experiments show high structural and electronic qualities of this new composite. The SIA allows for an atomic control of the distance between the graphene and the metal substrate that can be used as a top gate. Our results show potential for the next generation of graphene-based materials with tailored properties.Comment: 13 pages, 4 figures, to be published in Appl. Phys. Let