Adjacent Stripes Research Articles

Flexible micro-strain graphene sensors enhanced by laser-induced cracks for health monitoring

In-situ fabrication of patterned laser-induced graphene (LIG) has unique advantages, holding broad application prospects in the preparation of flexible electronic devices. However, a facile strategy is still demanded to improve the sensitivity of LIG-based sensors in detecting micro-strains. Herein, we propose a flexible graphene strain sensor enhanced by laser-induced cracks, which is capable of detecting small deformations. When the scanning spacing was expanded from 100 μm to 140 μm, abundant micro-cracks formed between adjacent LIG stripes, providing more sensing units. The open and close of cracks lead to significant change of resistance, enhancing the sensitivity of LIG-based sensors. The average gauge factors of sensors were improved to 98 (0–2 % strain), increasing nearly 20 times. The strain sensors exhibit high performance response to subtle signals of the human body. High-quality seismocardiography (SCG), pulse wave and respiration curves were achieved by our sensors, providing a lot of useful information for screening chronic diseases. Overall, this research highlights an effective method for fabricating high performance flexible strain sensors for long-term health monitoring.

Nonreciprocal magnonic directional coupler based on metal-coated YIG adjacent stripes

Unidirectional information transport is often realized in magnonic application using the filters, isolators, and circulators. In this Letter, we propose the simple design of the unidirectional magnonic coupler, which is realized as a laterally coupled yttrium–iron–garnet waveguide coated with a metal layer. We experimentally discover and numerically confirm that the proposed structure can exhibit unidirectional coupling, which can be easily controlled by the direction of the external magnetic field. At the same time, we show how the dynamic magnetization profile of the spin wave is varied with the change in the propagation direction to the opposite along the coupler. Brillouin light scattering reveals the variation of the spatial spin-wave profile, which is then used to extract the value of the coupling length. The experimental results are in good agreement with the results of the coupling length estimation from two methods: eingenmode analysis and Landau–Lifshits–Gilbert solution in parallel with the Maxwell equations. This opens up alternative ways to fabricate the non-reciprocal magnonic devices. In particular, we consider the operation of the unidirectional magnonic coupler as a multi-regime logic device.

A deep learning-based stripe self-correction method for stitched microscopic images

Stitched fluorescence microscope images inevitably exist in various types of stripes or artifacts caused by uncertain factors such as optical devices or specimens, which severely affects the image quality and downstream quantitative analysis. Here, we present a deep learning-based Stripe Self-Correction method, so-called SSCOR. Specifically, we propose a proximity sampling scheme and adversarial reciprocal self-training paradigm that enable SSCOR to utilize stripe-free patches sampled from the stitched microscope image itself to correct their adjacent stripe patches. Comparing to off-the-shelf approaches, SSCOR can not only adaptively correct non-uniform, oblique, and grid stripes, but also remove scanning, bubble, and out-of-focus artifacts, achieving the state-of-the-art performance across different imaging conditions and modalities. Moreover, SSCOR does not require any physical parameter estimation, patch-wise manual annotation, or raw stitched information in the correction process. This provides an intelligent prior-free image restoration solution for microscopists or even microscope companies, thus ensuring more precise biomedical applications for researchers.

Calibration of micro-channel plate detector in a Thomson spectrometer for protons and carbon ions with energies below 1 MeV.

The calibration of an ion detection system was carried out for protons and carbon ions from a few tens of keV up to about 1MeV energies. A Thomson spectrometer deflecting the particle beam accelerated from a laser plasma creates the ion spectra on a phosphor screen behind a micro-channel plate (MCP), which are recorded by a camera. During calibration, the ion spectra simultaneously hit the slotted CR-39 track detector installed in front of the MCP and, passing through the adjacent CR-39 stripes, the MCP. The calibration provides the ratio of the interpolated values between two consecutive stripes of the camera signal and the total number of particles recorded on the corresponding stripe of CR-39. The efficiency of proton detection by CR-39 was also measured in a conventional accelerator beam and found to drop by 20% below 100keV.

Harmonious Multi-branch Network for Person Re-identification with Harder Triplet Loss

Recently, advances in person re-identification (Re-ID) has benefitted from use of the popular multi-branch network. However, performing feature learning in a single branch with uniform partitioning is likely to separate meaningful local regions, and correlation among different branches is not well established. In this article, we propose a novel harmonious multi-branch network (HMBN) to relieve these intra-branch and inter-branch problems harmoniously. HMBN is a multi-branch network with various stripes on different branches to learn coarse-to-fine pedestrian information. We first replace the uniform partition with a horizontal overlapped partition to cover meaningful local regions between adjacent stripes in a single branch. We then incorporate a novel attention module to make all branches interact by modeling spatial contextual dependencies across branches. Finally, in order to train the HMBN more effectively, a harder triplet loss is introduced to optimize triplets in a harder manner. Extensive experiments are conducted on three benchmark datasets — DukeMTMC-reID, CUHK03, and Market-1501 — demonstrating the superiority of our proposed HMBN over state-of-the-art methods.

Intraoral 3-D Measurement by Means of Group Coding Combined With Consistent Enhancement for Fringe Projection Pattern

Intraoral 3D measurement can obtain digital impressions in real time. However, owing to saliva, enamel, metallic denture, etc., the quality of the captured 2D image using the intraoral equipment, which is used for feature measurement and 3D reconstruction, is usually degraded. In this paper, we propose a equipment with high performance for intraoral 3D measurement. First, group-multi-line coding algorithm instead of sinusoidal or gray code for fringe projection profilometry (FPP) was applied for stripe pattern decoding. The distance between adjacent stripes was large enough to avoid the scatter of the tooth. It can also overcome the shortcoming of sinusoidal-based phase computing, leading to accuracy degradation owing to scanner jittering. Second, a consistent stripe feature enhancement method is proposed. The stripe feature in the mirror, exposure, and low-contrast area was homogeneously enhanced. Consequently, an individual scene is reconstructed using more effective and accurate points. This not only improves the precision of point cloud registration, it also reduces the probability of mismatch and shortens the scanning time for a full-arch. Our results showed that the accuracy of intraoral 3D measurements conducted through the proposed equipment by using novel algorithms increased to 10 - 20 μm and the measurement efficiency increased to 30%.

Microtubule disruption upon CNS damage triggers mitotic entry via TNF signaling activation.

Repair after traumatic injury often starts with mitotic activation around the lesion edges. Early midline cells in the Drosophila embryonic CNS can enter into division following the traumatic disruption of microtubules. We demonstrate that microtubule disruption activates non-canonical TNF signaling by phosphorylation of TGF-β activated kinase 1 (Tak1) and its target IkappaB kinase (Ik2), culminating in Dorsal/NfkappaB nuclear translocation and Jra/Jun expression. Tak1 and Ik2 are necessary for the damaged-induced divisions. Microtubule disruption caused by Tau accumulation is also reported in Alzheimer's disease (AD). Human Tau expression in Drosophila midline cells is sufficient to induce Tak1 phosphorylation, Dorsal and Jra/Jun expression, and entry into mitosis. Interestingly, activation of Tak1 and Tank binding kinase 1 (Tbk1), the human Ik2 ortholog, and NfkappaB upregulation are observed in AD brains.

Strain-mediated tunability of spin-wave spectra in the adjacent magnonic crystal stripes with piezoelectric layer

We demonstrate that properties of spin-wave propagation in the adjacent magnonic crystal stripes with one of them in contact with a piezoelectric layer can be controlled by an external electric field. We perform microwave spectroscopy and employ a theoretical approach based on the analysis of the set of coupled wave equations. By considering incident and reflected waves in the first Brillouin zone, we calculate the reflection coefficients of the magnonic structure. Two narrow magnon bands are observed in the experiment, and their behavior with the variation of the electric field applied to the piezoelectric layer was shown. The finite-element calculations of the self-consistent eigenvalue problem elucidate how the influence of the piezoelectric layer can be modeled as a localized strain-induced internal magnetic field and its variation affects the spin-wave dispersion. Both the frequency shift and closing of a magnon band are detected in our measurements and confirmed by the simulations and the analytical approach. Therefore, we demonstrate the electric field control of the magnonic bands. Our results reveal the mechanism of the spin-wave spectra control in the coupled magnonic crystals. The results pave the way for the implementation of frequency selective magnonic devices based on a straintronic approach.

X-ray Computed Tomography for the ex-situ mechanical testing and simulation of additively manufactured IN718 samples

The aim of this work is to present the quantitative evaluation of the Additive Manufacturing (AM) laser powder bed fusion (L-PBF) process steps and validation of the FE (Finite Elements) simulation results using the X-ray Computed Tomography (XCT) based approach. The characterization of the production process was made using standard methods, including: laser light diffraction, optical and scanning electron microscopy, hardness examinations, and the investigation of mechanical properties. The XCT method was used to conduct the quality of powder feedstock, the influence of the L-PBF build strategy on the samples’ porosity, and also to evaluate a quantitative analysis of damage behavior before and after ex-situ mechanical testing. The porosity recorded for the powder feedstock was 0.2% and for test samples did not exceed 0.02%. The majority of the observed pores are aligned in patterns connected with the scanning strategy and were arranged in lines appearing along the borders between adjacent stripes. It was observed that increasing the resolution of the XCT scanning significantly influenced the mapping of the shape of pores and – to a lesser extent – the recorded porosity. The comparison of geometry deviations after numerical simulation and tensile test for FE models obtained with different XCT resolutions allowed to show differences in the geometry of experimentally and numerically damaged test samples.

Study on shallow donor-type impurities of GaN epilayer regrown by epitaxial lateral overgrowth technique

p-doped gallium nitride (GaN) regrowth by epitaxial lateral overgrowth using a SiO2 mask is studied. A comparison between SiO2 and Al2O3 masked p-GaN by cathodoluminescence spectroscopy and scanning electron microscopy indicates that donor-type impurities are related to the SiO2 mask. A domain peak of 3.25 eV induced by shallow-donor and acceptor transitions and the dark contrast of obtuse triangles have been detected in SiO2 masked p-type GaN. Secondary ion mass spectroscopy is simultaneously employed for the analysis of SiO2 and Al2O3 masked p-GaN and identifies that the source of donor-type impurities is from Si atoms. Furthermore, the experimental results of cross-sectional microstructures at different regrowth times have been investigated. It is found that the donor-type impurities tend to cluster in semi-polar 112¯2 facets before the coalescence at the bottom of adjacent triangular stripes starts. The explanation for the non-uniform distribution of impurities is that semi-polar 112¯2 facets exhibit more dangling bond densities than the (0001) plane, and the SiO2 mask exposed to the vapor phase would likely introduce more impurities before the coalescence of GaN stripes.

Combinatorial nanodot stripe assay to systematically study cell haptotaxis

Haptotaxis is critical to cell guidance and development and has been studied in vitro using either gradients or stripe assays that present a binary choice between full and zero coverage of a protein cue. However, stripes offer only a choice between extremes, while for gradients, cell receptor saturation, migration history, and directional persistence confound the interpretation of cellular responses. Here, we introduce nanodot stripe assays (NSAs) formed by adjacent stripes of nanodot arrays with different surface coverage. Twenty-one pairwise combinations were designed using 0, 1, 3, 10, 30, 44 and 100% stripes and were patterned with 200 × 200, 400 × 400 or 800 × 800 nm2 nanodots. We studied the migration choices of C2C12 myoblasts that express neogenin on NSAs (and three-step gradients) of netrin-1. The reference surface between the nanodots was backfilled with a mixture of polyethylene glycol and poly-d-lysine to minimize nonspecific cell response. Unexpectedly, cell response was independent of nanodot size. Relative to a 0% stripe, cells increasingly chose the high-density stripe with up to ~90% of cells on stripes with 10% coverage and higher. Cell preference for higher vs. lower netrin-1 coverage was observed only for coverage ratios >2.3, with cell preference plateauing at ~80% for ratios ≥4. The combinatorial NSA enables quantitative studies of cell haptotaxis over the full range of surface coverages and ratios and provides a means to elucidate haptotactic mechanisms.

3D printed agar/ calcium alginate hydrogels with high shape fidelity and tailorable mechanical properties

In this study, calcium alginate/agar (CA/Ag) 3D structures were printed as strip assembles with high resolution and tailorable mechanical properties by a thermal-assisted 3D printing method. Specifically, alginate and agar were combined to minimize the Barus effect, and further improved the printing resolution. The introduction of agar altered the rheological properties of the ink, such as increasing its viscosity to obtain a 3D printing structure with higher precision. The alginate chains were crosslinked by calcium ions, which connected different layers together and had good interface adhesion among layers in 3D printing constructs. In addition, after printing, the crosslinking of calcium alginate affected the swelling behavior and mechanical properties of printing gels. The width of extrusion gel stripes was close to the diameter of needle, demonstrating that the printing resolution is well controlled by minimizing the Barus effect of concentrated solution. Furthermore, the printed gel structures showed low cytotoxicity, indicating that these biocompatible 3D printed structures are promising substitutes for tissue engineering. Most importantly, soft polyacrylamide (PAAm) network was introduced into 3D printed CA/Ag hydrogels to toughen interfacial surfaces between adjacent stripes by combination of rigid calcium alginate network and soft PAAm network. These 3D printed hydrogels with excellent mechanical properties, high compatibility and high shape fidelity can be regarded as a potential candidate in bio-medical field.

Study on the junction zone of NiTi shape memory alloy produced by selective laser melting via a stripe scanning strategy

In our previous study, NiTi shape memory alloy with excellent tensile properties (total elongation up to 15.6%) was fabricated by selective laser melting (SLM) through a stripe scanning strategy. Junction zone is inevitable in the SLM-fabricated NiTi parts produced using the stripe scanning strategy, which appears between adjacent stripes, and the thermal history of the junction zone is significantly different from that of other areas. In this study, the microstructure, phase transformation behavior, and mechanical properties of the junction zone and non-junction zone were studied. Compared with the non-junction zone, the junction zone exhibits higher phase transformation temperatures and hardness. The refinement of microstructure, more random crystallographic orientations and high-density of pore defects are observed in the junction zone of the SLM-fabricated NiTi alloy. Besides, we studied the effect of different sizes of the junction zone on the tensile mechanical properties of the SLM-NiTi alloy. It is demonstrated that the fracture strength of SLM-NiTi alloy increases with the increase of the proportion of the junction zone. In this work, we discussed the mechanisms of the phenomena in detail.

Strain reconfigurable spin-wave transport in the lateral system of magnonic stripes

We demonstrate the possibility of controlling dipole spin-wave coupling in the lateral array of ferromagnetic stripes using local strains. Lateral system of magnonic stripes with a piezoelectric layer is fabricated and tested with microwave and Brillouin light scattering spectroscopy. The mechanisms of controlling the dipole coupling of spin waves by elastic strains localized in the region of maximums of the electric field strength are revealed. It is shown that when the absolute value and sign of the electric field are changed, it is possible to effectively control the properties of the propagating spin waves and the spatial distribution of the intensity of the dynamic magnetization in the lateral structure. We emphasize that the spin-wave intermodal coupling can be tuned with the external electric field in the adjacent magnonic stripes. Formation of channel for spin-wave edge mode propagation is observed experimentally in the vicinity of the gap between adjacent stripes. Effective control of the spin-wave coupling by changing the gap is demonstrated. From an applied point of view, the results can be used in information processing devices with electric and magnetic field tunability.

Ways to Correct the Errors in Posture of Multi-beam Sounding Resulted from Water Flow

Multi-beam bracket deformation is caused by factor like water flow and speed of ship. Such deformation also leads to the axle offset of relative attitude indicator of transducer, which may influence the accuracy of results. As for this phenomenon, the paper proposes a method that calculates water velocity and output speed of ship according to the navigation data, in order to fit the attitude deviation and correct the results of depth measurement. First of all, water velocity and output speed of ship of two adjacent stripes without abnormal sounding results in the testing zone in good sea condition are calculated respectively according to navigation data, and then the errors in posture of these two stripes in different time are worked out respectively based on discrepancy in elevation of the overlapping portions of the stripes; secondly, a modifier formula of water velocity, output speed of ship and errors in posture is formulated; finally, this formula is applied to solving errors in posture and correcting the sounding data of stripes in the testing zone. According to the experimental results, the proposed method can eliminate errors in posture effectively, with the average of discrepancy in elevation reduced from 0.188m (before) to 0.032m (after). The stripe splicing effect is improved and the data accuracy is enhanced enormously.

Alternative Models of Zebra Patterns in the Event on June 21, 2011

The analysis of the spectral characteristics of the burst radio emission on June 21, 2011 was carried out on the basis of an improved methodology for determining harmonic numbers for the corresponding stripes of the zebra structure. By using the parameters of the zebra structure in the time-frequency spectrum and basing on the double-plasma resonance model, the magnetic field and its dynamics, electron density, and the time variation of the distance between the stripes with harmonics \(s = 55\) and 56 and adjacent stripes near the frequency ≈183 MHz have been determined in the burst generation region. The relationships between the scale characteristics of the field and the density along and across the axis of the power tube and their dependence on time have been also determined. The field obtained (1.5 G for the first harmonic and 0.75 G for the second harmonic of the plasma frequency) turned out to be so small that, firstly, it fails to explain the dynamic features of the spectrum based on MHD waves, and secondly, it results in large values for plasma beta (>1). Other possible difficulties of the generation mechanism of bursts with zebra pattern based on the double-plasma resonance are also noted. Another possible mechanism, with whistlers, explains qualitatively the main observational characteristics of this zebra. The magnetic field required in this case is about 4.5 G, and the plasma beta is 0.14, which fully corresponds to the coronal conditions.

Uncompensated Polarization in Incommensurate Modulations of Perovskite Antiferroelectrics.

Complex polar structures of incommensurate modulations (ICMs) are revealed in chemically modified PbZrO_{3} perovskite antiferroelectrics using advanced transmission electron microscopy techniques. The Pb-cation displacements, previously assumed to arrange in a fully compensated antiparallel fashion, are found to be either antiparallel, but with different magnitudes, or in a nearly orthogonal arrangement in adjacent stripes in the ICMs. Abinitio calculations corroborate the low-energy state of these arrangements. Our discovery corrects the atomic understanding of ICMs in PbZrO_{3}-based perovskite antiferroelectrics.

Precise Position Detection of Linear Motor Movers Based on Extended Joint Transformation Correlation

The extended joint transformation correlation (EJTC) algorithm is proposed in this paper to meet the high-precision and anti-interference requirements of linear motor mover position measurement. An image measurement system for linear motor mover position is established. Stripe image movement sequences are captured using a high-speed camera. First, the image is preprocessed using a bilateral filtering method. Second, the joint power spectral function of adjacent stripe images is obtained on the basis of the joint transform correlation method. The zero-order diffraction peaks are eliminated, and interference from cross-correlated peak side lobes is avoided. Third, subpixel positioning is obtained using the oversampled discrete Fourier transform. Finally, the actual displacement of the stripe images can be obtained by combining the system calibration coefficients. An experimental measurement platform for a linear motor mover is established to verify the validity of the EJTC algorithm. The EJTC shows high measurement accuracy and strong anti-interference ability.

Pinning-Depinning Mechanism of the Contact Line during Evaporation of Nanodroplets on Heated Heterogeneous Surfaces: A Molecular Dynamics Simulation.

Droplet evaporation on heterogeneous or patterned surfaces has numerous potential applications, for example, inkjet printing. The effect of surface heterogeneities on the evaporation of a nanometer-sized cylindrical droplet on a solid surface is studied using molecular dynamics simulations of Lennard-Jones particles. Different heterogeneities of the surface were achieved through alternating stripes of equal width but two chemical types, which lead to different contact angles. The evaporation induced by the heated substrate instead of the isothermal evaporation is investigated. It is found that the whole evaporation process is generally dominated by the nonuniform evaporation effect. However, at the initial moment, the volume expansion and local evaporation effects play important roles. From the nanoscale point of view, the slow movement of the contact line during the pinning process is observed, which is different from the macroscopic stationary pinning. Particularly, we found that the speed of the contact line may be not only affected by the intrinsic energy barrier between the two adjacent stripes ( ũ) but also relevant to the evaporation rate. Generally speaking, the larger the intrinsic energy barrier, the slower the movement of the contact line. At the specified temperature, when ũ is less than a critical energy barrier ( ũ*), the speed of the contact line would increase with the evaporate rate. When ũ > ũ*, the speed of the contact line is determined only by ũ and no longer affected by the evaporation rate at different stages (the first stick and the second stick).

Magnon Straintronics to Control Spin-Wave Computation: Strain Reconfigurable Magnonic-Crystal Directional Coupler

The effect of electrical field control of the spin-wave spectrum in adjacent magnonic crystals stripes was investigated by micromagnetic simulation, microwave spectroscopy, and Brillouin light scattering (BLS). The electric-field-induced dipolar coupling between magnetic stripes leads to the formation of symmetric and antisymmetric collective modes in the spectra of propagating spin waves. In particular, the strain-induced variation of the spin-wave coupling length in the stripe, predicted by micromagnetic simulation and measured by BLS, show the possibility of application of a lateral array of magnonic crystals as tunable microwave directional couplers, power dividers, and spin-wave demultiplexers, which can be used simultaneously as an interconnection unit in reconfigurable magnonic networks.