Fringe Structure Research Articles

TTFDNet: Precise Depth Estimation from Single-Frame Fringe Patterns.

This work presents TTFDNet, a transformer-based and transfer learning network for end-to-end depth estimation from single-frame fringe patterns in fringe projection profilometry. TTFDNet features a precise contour and coarse depth (PCCD) pre-processor, a global multi-dimensional fusion (GMDF) module and a progressive depth extractor (PDE). It utilizes transfer learning through fringe structure consistency evaluation (FSCE) to leverage the transformer's benefits even on a small dataset. Tested on 208 scenes, the model achieved a mean absolute error (MAE) of 0.00372 mm, outperforming Unet (0.03458 mm) models, PDE (0.01063 mm) and PCTNet (0.00518 mm). It demonstrated precise measurement capabilities with deviations of ~90 μm for a 25.4 mm radius ball and ~6 μm for a 20 mm thick metal part. Additionally, TTFDNet showed excellent generalization and robustness in dynamic reconstruction and varied imaging conditions, making it appropriate for practical applications in manufacturing, automation and computer vision.

Boosting capacitive deionization of monovalent and hardness ions using Ti3C2Tx MXene as an intercalation-type pseudocapacitive electrode

MXene is a promising electrode material for energy storage and capacitive deionization (CDI) applications. In this study, a viable approach was developed to synthesize Ti3C2Tx at different LiF/Ti3AlC2 mass ratios of 0.5 – 2.0 for the enhanced CDI to remove different cations including hardness (Mg2+ and Ca2+), salt (Na+), and ammonium (NH4+) ions. The Ti3C2Tx was fabricated using the hydrothermal method in the presence of LiF and HCl. The optimal mass ratio of 1.0 results in the formation of hydrophilic and well-delaminated nanosheets. Moreover, the Ti3C2Tx-1 shows an interconnected meso-macroporous structure with a specific surface area of 48.4 m2/g. The Ti3C2Tx MXene exhibits an exceptional electrochemical performance with a specific capacitance of 540 F g−1 at 5 mV s−1 in the presence of 1 M H2SO4. A remarkable desalination performance with the salt adsorption capacity (SAC) of 39.7 mg g−1 is obtained. The well-suited lattice fringe and inter-connected porous structure of the Ti3C2Tx nanosheets accelerate the electron transport, which can maintain the cyclability over 50 cycles. This enhanced electron transport leads to an improved deionization capability during the CDI process. Moreover, the Ti3C2Tx-based CDI device exhibits prominent selectivity for hardness ions with SACs of 43.8 and 39.5 mg g−1 for Ca2+ and Mg2+, respectively. The SAC of NH4+ can also be up of 39.7 mg g−1 at 1000 mg L−1. Results in this study clearly elaborate the promising potentiality for the utilization of MXene as an effective electrode material for desalination and other electrochemical applications.

Effect of NH3 addition on soot morphology and nanostructure evolution in laminar ethylene diffusion flame

Ammonia, as a carbon neutral alternative fuel, has attracted wide attention. However, due to the defects in the combustion performance of pure ammonia, it is still necessary to further solve this problem in practical utilization. The purpose of this paper is to study the influence of ammonia on the morphology of soot and the evolution of nanoparticle structure in laminar flame of ethylene. In this work, the soot collected by thermophoresis probe was observed by the high resolution transmission electron microscope (HRTEM), and the image information in HRTEM images was statistically processed, and the graphitization degree of soot was measured by X-ray diffraction (XRD) spectrum of soot samples. The experimental results show that the addition of ammonia can inhibit the growth of soot nuclei and delay the formation of incipient soot, and has different effects on the evolution of soot morphology and structure in ethylene flame. It is noteworthy that the soot samples collected in the upstream part of the ammonia-doped flame show more mature core–shell structure in HRTEM images and more graphitized XRD diffraction data than those collected in pure ethylene flame. The main reason may be the chemical effect of ammonia and the thermal effect caused by the reduction of flame radiation loss, which have different effects on the nanostructure and morphology of soot at different stages of soot formation. Fringe structure model is used to describe and explain the influence of soot in flame with height before and after ammonia doped.

Micro/nanostructured amorphous TiNbZr films to enhance the adhesion strength and corrosion behavior of stainless steel

To improve the corrosion resistance of key components and ensure the service safety of marine equipment, here we combined femtosecond (fs) laser fabrication and magnetron sputtering deposition to develop micro/nanostructured amorphous TiNbZr films. Analysis of the compositional, microstructural, corrosion, and mechanical properties was conducted. The results showed that the TiNbZr films were amorphous, and spherical TiNbZr nanoparticles uniformly covered the fs laser-induced periodic fringe structure. A complex hierarchical micro/nanostructure was formed that was hydrophobic and showed enhanced adhesion strength. The TiNbZr films deposited on fs laser-treated substrates provided the best corrosion resistance, showing a self-corrosion current density of 116 nA/cm2, excellent passive ability, and pitting resistance. The microscratch test revealed that the micro/nanostructures doubled the binding strength of the TiNbZr/316L interface due to the compositional and structural gradients induced by an approximately 20 nm transition layer formed during fs laser processing. This work provides a new method for obtaining anti-corrosion films with a high adhesion strength for marine applications.

Characterization of biodiesels and tire derived particulate matters in morphology and nanostructure

Particulate Matters (PM) are known to be dangerous to human health and the environment. Regulations have been set to limit PM levels from vehicles, including compression ignition engine vehicles. The effect of increasing biodiesel content in the fuels has been investigated with respect to the PM using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). PM from tire emissions were compared against diesel PM using SEM, energy dispersive x-ray spectroscopy (EDS), TEM, particle size analysis, x-ray diffraction (XRD), and Raman spectroscopy (RS). The SEM and TEM show that increasing the biodiesel content decreased the size of the PM agglomerate particles, primary particles, and fringes. The EDS, RS, and XRD show that Tire PM are mostly carbon with silicon, calcium, zinc, and other various trace elements. They also allow comparisons with diesel PM for the carbon nanostructure. The particle size analysis shows that Tire PM are generally larger than engine derived PM. The TEM showed that the nanostructure of the carbonaceous Tire PM was the same fringe structure as the engine derived PM. The Tire PM was successfully characterized using similar methods as engine derived soot. There is strong relationship between the increasing of biodiesel content and reduction of agglomerate size, primary particle size and average fringe length.

Nonhomogeneous clutter suppression based on terrain elevation interferometric phase compensation in multi-satellite formation systems

In multi-satellite formation synthetic aperture radar (SAR) systems, the nonhomogeneous clutter problem arising due to the terrain elevation interferometric phase is a crucial factor that degrades clutter suppression performance. We propose a clutter suppression method based on terrain interferometric phase compensation (TIPC) that can overcome this problem. The method can be summarised as a rough-and-refined two-step phase compensation framework. In the rough-compensation stage, the terrain interferometric phase is estimated using similar phase samples in a local area. To ensure that more candidate samples are considered, a novel sample-selection window is designed based on fringe direction and density; its shape and size can be adjusted adaptively based on the fringe morphology. For refined topographic phase compensation, an error feedback weighting correction structure is designed to compensate for the fringe detail loss. The weighting coefficient is constructed based on coherence, phase residual distribution, and fringe structure features, which can be adapted to adjust the contribution of the phase estimation error. Moreover, to improve the topographic phase compensation performance, the proposed method can be applied iteratively. Finally, clutter suppression was performed after the TIPC processing. The experimental results demonstrate that the proposed method can obtain higher topographic phase compensation precision and better clutter suppression performance than conventional methods.

3D Growth of Intragranular Pearlite in an Aged 100Mn13 Steel

The morphology and microstructure of intragranular pearlite in 100Mn13 high‐carbon, high‐manganese steel aged at 600 °C are observed by a scanning electron microscope (SEM) and transmission electron microscope (TEM) and analyzed, and growth models describing the morphology and growth process in 3D space are proposed. The results show that pearlite could nucleate directly in the austenite grain and present a 3D morphology after deep etching, and ferrite and cementite in pearlite keep the orientation relationship (OR) with austenite, , , , and . Also, the overall continuous ledges at the lamellar ferrite surface and end surround the whole ferrite lamellae, corresponding to a fringe structure and a curved frontier interface in 2D space, which shows a terraced morphology in 3D space. The different structures of the α/γ interface in 3D directions result in different growth rates of ferrite lamellae, that is, edgewise grows fastest along the direction of due to the incoherent interface composed of with a 28% mismatch, and sidewise grows slowest along the direction of due to the coherent interface composed of with a 1.9% mismatch.

Super-Resolution Based on Generative Adversarial Network for HRTEM Images

As an important tool to study the microstructure and properties of materials, High Resolution Transmission Electron Microscope (HRTEM) images can obtain the lattice fringe image (reflecting the crystal plane spacing information), structure image and individual atom image (which reflects the configuration of atoms or atomic groups in crystal structure). Despite the rapid development of HTTEM devices, HRTEM images still have limited achievable resolution for human visual system. With the rapid development of deep learning technology in recent years, researchers are actively exploring the Super-resolution (SR) model based on deep learning, and the model has reached the current best level in various SR benchmarks. Using SR to reconstruct high-resolution HRTEM image is helpful to the material science research. However, there is one core issue that has not been resolved: most of these super-resolution methods require the training data to exist in pairs. In actual scenarios, especially for HRTEM images, there are no corresponding HR images. To reconstruct high quality HRTEM image, a novel Super-Resolution architecture for HRTEM images is proposed in this paper. Borrowing the idea from Dual Regression Networks (DRN), we introduce an additional dual regression structure to ESRGAN, by training the model with unpaired HRTEM images and paired nature images. Results of extensive benchmark experiments demonstrate that the proposed method achieves better performance than the most resent SISR methods with both quantitative and visual results.

Self-registration shape measurement based on fringe projection and structure from motion.

As an accurate and efficient shape measurement method, fringe-projection-based three-dimensional (3D) reconstruction has been extensively studied. However, patchwise point cloud registration without extra assistance is still a challenging task. We present a flexible and robust self-registration shape measurement method based on fringe projection and structure from motion (SfM). Other than ordinary structured-light measurement devices in which the camera and the projector are rigidly connected together, the camera and the projector in our method can be moved independently. An image-capturing scheme and underlying image-matching strategy are proposed. By selectively utilizing some sparse correspondence points across the fringe images as virtual markers, the global positions of the camera and the projector corresponding to each image are calculated and optimized under the framework of SfM. Dense global 3D points all over the object surface are finally calculated via forward intersection. Experimental results on different objects demonstrate that the proposed method can obtain a self-registered 3D point cloud with comparable accuracy to the state-of-the-art techniques by using only one camera and one projector, requiring no post-registration procedures and no assistant markers.

Design of a large aperture, tunable, Pancharatnam phase beam steering device.

Replacing mechanical optical beam steering devices with non-mechanical electro-optic devices has been a long-standing desire for applications such as space-based communication, LiDAR and autonomous vehicles. While promising progress has been achieved to non-mechanically deflect light with high efficiency over a wide angular range, significant limitations remain towards achieving large aperture beam steering with a tunable steering direction. In this paper, we propose a unique liquid crystal based Pancharatnam Phase Device for beam steering which can provide both tunability and a fast response times in a format scalable to large apertures. This architecture employs a linear array of phase control elements to locally control the orientation of the liquid crystal director into a cycloidal pattern to deflect transmitted light. The PCEs are comprised of a fringe field switching electrode structure that can provide a variable in-plane electric field. Detailed modeling of the proposed design is presented which demonstrates that such a device can achieve a high degree of uniformity as it rotates the LC molecules over the 180 ° angular range required to create a Pancharatnam phase device.

Геометрооптический механизм восстановления волнового фронта

The mechanism of wavefront reconstruction by a geometric-optical reflection of reconstructing light from surfaces with constant phase differences between the object and reference waves used to record the interference fringe structure in the medium bulk is analyzed. This mechanism is compared with the holographic one. Experiments in volume medium and in planar optical waveguide were carried out. Several types of achromatic optical elements are proposed. The optoacoustic focusing element, which can create a great local stress in a special shaped area inside the matter, is discussed. The possibility of the ultrashort pulse temporal reconstruction is demonstrated.

Difference in structural chemistry of non-coking and coking coal using acid treatment demineralization technique

ABSTRACT Recently, the structural information about non-coking and coking coal has attracted pronounced interest for sustainable utilization of poor coking coal in different industries specifically for steel industry like Tata Steel. In the present work, demineralization techniques via acid treatment (HCl-HF) are effective to remove mineral phase from coal. The difference in carbon chemistry of non-coking (CDPCI), weakly coking (Curragh SS), and prime coking coals (Illawarra and Jamadoba) has been studying through advanced characterization methods like petrography, TGA-DTG, FTIR spectroscopy, X-ray diffraction, Raman, 13C solid-state NMR, FESEM, and TEM. These advanced characterization techniques offer comparative structural information of different coal through the distribution of individual coal maceral and mineral grains with their rank (petrographic study), functional group study along aliphatic-aromatic structural relationship measurement (FTIR), crystalline/graphitic nature of carbon (XRD & Raman) with oxygenated carbon skeletal structural information (Solid State 13C NMR), aromatic-aliphatic cross-linking behavior (FESEM) and their orientation toward lattice fringe structure (TEM).

EBSD and CL Study of Deformed Quartz Grains in Rocks: An Example for one Strain Fringe Structure From Iron Quadrangle.

Kinematic indicators, including certain strain fringes, represent an important group of structures related to the progressive deformation in rocks. The evolution of these fibrous textures can be explained by the combination of multiple mechanisms of deformation and fluid flow, mainly controlled by the orientation of the strain field and the morphology of the grains. In general, the observations are done with an optical microscope and compared with computational models of growth. This work proposes a combination of crystallographic and cathodoluminescence data obtained in rocks from banded iron formations of the Iron Quadrangle in Brazil to represent an example of how complementary analytical techniques can be useful to understand geological problems. The chosen sample exhibits a strain fringe structure of quartz around a clast of magnetite partially transformed into goethite and hematite. Through the crystallographic data it was possible to identify the grain boundary morphology and domains of low deformation areas. On the other hand, the cathodoluminescence signal evidenced the occurrence of grains with a higher concentration of crystalline defects.

Rayleigh-Sommerfeld diffraction on a subwavelength scale: Theories and a resolution criterion

Classical resolution criteria such as Rayleigh's and Sparrow's are based on the fringe structure produced by Fresnel diffraction or Fraunhofer diffraction. However, these two diffraction theories are based on the assumption of large-aperture scale and are thus incapable of describing the diffraction of subwavelength structure. We find a singularity near the incident wave vector ${k}_{0}$ in a subwavelength aperture by considering Rayleigh-Sommerfeld diffraction. The diffraction fringe structure disappears once the aperture scale is smaller than a threshold value. A two-point resolution criterion unrelated to the fringe structure is proposed based on the second-order derivative of the field structure. Numerical results indicate that, for the illumination wavelength of $\ensuremath{\lambda}=500\phantom{\rule{0.16em}{0ex}}\mathrm{nm}$, resolution of two 100-nm rectangular holes under near-field Rayleigh-Sommerfeld diffraction is improved by about 300 and 20% in the $x$ and $z$ directions, respectively, compared with the Sparrow criterion, while the lateral resolution limit is reduced to 35 nm.

A study of Chinese regional hierarchical structure based on surnames

We use isonymic distance to measure the dissimilarity in surname structure between populations of Chinese provinces, and we employ the minimum spanning tree (MST) and the single linkage cluster analysis (SLCA) to investigate the hierarchical structure of Chinese provinces and present its corresponding geographical features. We find diverse discrepancies in the averaged isonymic distance among provinces that are attributed to the heterogeneous surname distributions. The MST displays a core–fringe structure with Henan, Anhui, and Hubei making up the core, and several border provinces on the fringe. The degree centrality list in the MST reveals some “local centers” that act as regional economic centers. On the other hand, the geographical layout of MST reflects the historical “Rush to Northeast” mass migration, as well as the blocking effect of the Qinling–Huaihe line that separates north and south China. The clustering results derived from the SLCA show nine groups of provinces in which each group is geographically continuous.

Quantum Interference of Glory Rescattering in Strong-Field Atomic Ionization.

During the ionization of atoms irradiated by linearly polarized intense laser fields, we find for the first time that the transverse momentum distribution of photoelectrons can be well fitted by a squared zeroth-order Bessel function because of the quantum interference effect of glory rescattering. The characteristic of the Bessel function is determined by the common angular momentum of a number of semiclassical paths termed as glory trajectories, which are launched with different nonzero initial transverse momenta distributed on a specific circle in the momentum plane and finally deflected to the same asymptotic momentum, which is along the polarization direction, through post-tunneling rescattering. Glory rescattering theory based on the semiclassical path-integral formalism is developed to address this effect quantitatively. Our theory can resolve the long-standing discrepancies between existing theories and experiments on the fringe location, predict the sudden transition of the fringe structure in holographic patterns, and shed light on the quantum interference aspects of low-energy structures in strong-field atomic ionization.

Crystallization of calcium silicate hydrates on the surface of nanomaterials

AbstractThe poorly crystalline calcium silicate hydrate (C‐S‐H) is the primary binding phase in portland cement concrete. In this paper, the influence of adding anatase phase nano‐TiO2, nano‐SiO2, graphene oxide (GO), and multiwalled carbon nanotubes (CNT) on the crystallization and morphology of C‐S‐H are systematically investigated through tests. C‐S‐H gels were prepared using the double decomposition method, and the nanomaterial additions of nano‐TiO2, nano‐SiO2, GO, and CNT were 2 wt%, 2 wt%, 0.5 wt%, and 0.5 wt%, respectively. X‐ray diffraction (XRD) results show that a more crystalline nanostructure of C‐S‐H is induced by the addition of nano‐TiO2 or GO. This phenomenon is further confirmed by the transmission electron microscopy (TEM) observations. The TEM observations demonstrate that C‐S‐H would grow on the crystal face of TiO2 to form nanocrystalline regions with a lattice fringe spacing of 3.0 Å. When incorporated with GO, it will form a square lattice structure with a lattice constant of 3.1 Å on the surface of GO and later change to the lattice fringe structure with a spacing of 3.1 Å on the region bit away the GO surface. However, when adding nano‐SiO2 or CNT, these nanocrystalline regions are not observed. Further characterization through scanning electron microscopy (SEM) and atomic force microscopy (AFM) has been performed to investigate the effect of nanomaterials on C‐S‐H morphology. Different nanomaterials take a different morphology of C‐S‐H: sheet‐shape structures for pure C‐S‐H, rod‐shape with for C‐S‐H with nano‐TiO2, and granular agglomeration for C‐S‐H with nano‐SiO2. C‐S‐H with GO or CNT forms a structure of C‐S‐H growing on the templates.

Features of a Self-Mixing Laser Diode Operating Near Relaxation Oscillation.

When a fraction of the light reflected by an external cavity re-enters the laser cavity, both the amplitude and the frequency of the lasing field can be modulated. This phenomenon is called the self-mixing effect (SME). A self-mixing laser diode (SM-LD) is a sensor using the SME. Usually, such LDs operate below the stability boundary where no relaxation oscillation happens. The boundary is determined by the operation condition including the injection current, optical feedback strength and external cavity length. This paper discovers the features of an SM-LD where the LD operates beyond the stability boundary, that is, near the relaxation oscillation (RO) status. We call the signals from such a SM-LD as RO-SM signals to differentiate them from the conventional SM signals reported in the literature. Firstly, simulations are made based on the well-known Lang and Kobayashi (L-K) equations. Then the experiments are conducted on different LDs to verify the simulation results. It shows that a RO-SM signal exhibits high frequency oscillation with its amplitude modulated by a slow time varying envelop which corresponds to the movement of the external target. The envelope has same fringe structure (half-wavelength displacement resolution) with the conventional SM signals. However, the amplitudes of the RO-SM signals are much higher compared to conventional SM signals. The results presented reveal that an SM-LD operating near the RO has potential for achieving sensing with improved sensitivity.

Far-field diffraction of vortex grating

In this paper, we study theoretically and experimentally the far-field diffraction of amplitude vortex grating. The analytic expression of the diffraction intensity distribution is deduced according to Bessel function and its recursion formula, and the dependence relation of the diffraction on the parameters of grating is exhibited. The numerical simulations indicate the diffraction patterns consist of two characteristic components, namely, the inner spot and the periphery turbine-like fringes. The number of grating lines and their rotation direction determine the structure of the periphery turbine-like fringes. The density of the grating lines influences the radial size of the turbine-like fringe structure, and the hard-edged aperture controls the compaction of the fringes besides limiting the diffraction intensity. The practical experimental results verify these conclusions. The study of this paper will be helpful for the understanding the diffraction characteristics of vortex grating and regulating artificially the intensity distribution of the beam.

Viewing angle controllable fringe and in-plane switching vertical alignment LCD

A viewing angle controllable fringe and in-plane switching vertical alignment liquid crystal display (LCD) structure has been proposed. To realise the change from wide viewing angle (WVA) to narrow viewing angle (NVA) in a single LCD panel, the bias voltage is applied on the common electrode, and NVA can decreases with the increasing bias voltage. In WVA mode, the viewing angle cone (contrast ratio larger than 1000:1) is almost 70° and the contrast ratio is larger than 100:1 in arbitrary azimuthal directions. In NVA mode, the viewing angle cone (10:1) can continuously and uniformly change from 40° to 20°.