Stripe Pattern Research Articles

Harvest of Cell-Only Muscle Fibers Using Thermally Expandable Hydrogels with Adhesive Patterns.

Muscle tissue engineering has been the focus of extensive research due to its potential for numerous medical applications, including ex vivo actuator development and clinical treatments. In this study, we developed a method for harvesting muscle fiber in a floatable and translocatable manner utilizing thermally expandable hydrogels with a chemically patterned polydopamine (PD) layer generated by microcontact printing (μCP). The μCP of PD on the hydrogel facilitated the formation of stripe patterns with varying widths of printed/nonprinted area (50/50, 100/100, and 200/200 μm). The spatially controlled adhesion of C2C12 myoblasts on the PD patterns produced clearly distinguishable muscle fibers, and translocated muscle fibers exhibited preserved extracellular matrix and junction proteins. Furthermore, the development of anisotropic arrangements and mature myotubes within the fibers suggests the potential for functional control of engineered muscle tissues. Overall, the muscle fiber harvesting method developed herein is suitable for both translocation and floating and is a promising technique for muscle tissue engineering as it mimics the structure-function relationship of natural tissue.

Anisotropic reversing motion in laser-induced periodic surface structures

Observation of the evolution process of laser-induced periodic surface structure (LIPSS) will provide clues to its formation mechanism. We constructed a pulse-by-pulse image capture setup using oil-immersion optical microscopy with which we observed the evolution process on a coverslip of borosilicate glass, finding three LIPSS patterns: stripe patterns parallel and perpendicular to the electric field of the laser pulse, and a dot pattern. Furthermore, “reversing” motion was observed, that is, bright and dark interchange from pulse to pulse. The reversing motion had remarkable anisotropy, moving only perpendicular to the electric field of the laser pulse.

Differentiable Stripe Patterns for Inverse Design of Structured Surfaces

Stripe patterns are ubiquitous in nature and everyday life. While the synthesis of these patterns has been thoroughly studied in the literature, their potential to control the mechanics of structured materials remains largely unexplored. In this work, we introduce Differentiable Stripe Patterns---a computational approach for automated design of physical surfaces structured with stripe-shaped bi-material distributions. Our method builds on the work by Knöppel and colleagues [2015] for generating globally-continuous and equally-spaced stripe patterns. To unlock the full potential of this design space, we propose a gradient-based optimization tool to automatically compute stripe patterns that best approximate macromechanical performance goals. Specifically, we propose a computational model that combines solid shell finite elements with XFEM for accurate and fully-differentiable modeling of elastic bi-material surfaces. To resolve non-uniqueness problems in the original method, we furthermore propose a robust formulation that yields unique and differentiable stripe patterns. We combine these components with equilibrium state derivatives into an end-to-end differentiable pipeline that enables inverse design of mechanical stripe patterns. We demonstrate our method on a diverse set of examples that illustrate the potential of stripe patterns as a design space for structured materials. Our simulation results are experimentally validated on physical prototypes.

A sparse dictionary representation approach for anti-scattering grid artifact removal in X-ray images

The aim of this work is to introduce a new joint estimation approach for anatomical content and artifacts in digital radiography. Herein, we apply this approach to the anti-scattering grid suppression problem. These grids are generally used in low-dose radiography to improve the image contrast by absorbing the scattered radiation. However, they introduce an irregular stripe pattern in the clinical images which can hinder the diagnosis made by the radiologist.The problem is tackled in a sparse dictionary representation framework with an observation and prior models accounting for the physical model of image contents. Thus, the anatomical content is supposed to be sparsely represented by a Fourier or K-SVD dictionary. Furthermore, the artifact is modeled by a frequency dictionary. In addition, the noise is modeled by a locally stationary Gaussian distribution with zero mean and unknown variance. The joint estimation of all the projections is then performed using two methods: Beam-forming (IAA) and Bayesian (SUBLIM). Moreover, patch-wise processing is applied to avoid models’ errors due to spatial variations of the clinical contents and the artifact.IAA and SUBLIM performance is demonstrated for the anti-scattering grid extraction problem using experimental and real clinical images. The proposed methods remove gridline artifacts while maintaining the image details and avoiding ringing artifacts. In addition, they produce better results compared to the conventional filtering approaches, especially when the metallic materials are present in or on the patients. SUBLIM outperforms IAA in those regions thanks to a better clinical content model and physical noise prior.

Numerical Characterization of Magnetic Vortex Probe Imaging for Magnetic Force Microscopy

We study theoretically the performance and limitations of the magnetic vortex probe for magnetic force microscopy (MFM). In the ideal case, the only magnetically active part of the probe is the magnetic vortex core (VC) existing in the center of a Permalloy (Py) disk located at the apex of a non-magnetic tip. Such VC can be effectively characterized as a point dipole with the magnetic moment of the order of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-17</sup> Am <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> embedded about 20 nm inside the disk, which is similar to the commercial low-momentum MFM probes. In addition to the standard probes, the ideal VC probe offers high durability and a well-controlled magnetic moment suitable for quantitative MFM. However, since the VC probe is made of magnetically soft material its magnetization profile and the resulting MFM image can be deformed by the stray field of the sample. Therefore, the VC probe is suited for imaging the samples with small domain sizes which generate low stray fields. We numerically examine VC imaging of typical magnetic samples, i.e. domain arranged as a single circular dot, stripe patterns, and the chessboard. We determine the limiting dimensions of the domains that can be correctly imaged by the VC tip of optimal parameters. In general, we can conclude that MFM imaging by VC probes gives reasonable results for the samples with domains with lateral dimensions up to 100 nm.

Superpixel-Based Stripe Noise Removal for Satellite Imageries

This work introduces a novel noise removal algorithm for satellite imageries based on superpixel segmentation followed by statistics-based filtering. The algorithm worked in three main steps. First, the noisy input image was divided into subregions by employing simple linear iterative clustering (SLIC)-based superpixel segmentation. Then, the statistical property of each subregion was calculated, including their standard deviations and maximum values. Last, an adaptive statistics-based stripe noise removal was performed for each subregion by constructing adaptive filter sizes according to calculated properties. The algorithm was tested using real satellite imageries taken by the LAPAN-A2 and LAPAN-A3 satellites. Its performance was then compared to three existing methods in terms of image quality and computation speed. Extensive experiments on two datasets of 3-channel images captured by the LAPAN-A2 satellite showed that the algorithm was capable of reducing the stripe pattern as measured using the peak-signal-to-noise-ratio (PSNR) metric without introducing additional artifacts, which commonly appeared on over-corrected regions. Moreover, compared to existing methods, the proposed algorithm ran 42 to 103 times faster and provided better image quality by 2.46%, measured using the structural similarity metric (SSIM). The code of this work and the datasets used for the testing are publicly available on www.github.com/dancingpixel/SPSNR.

Photonic crystals with rainbow colors by centrifugation-assisted assembly of colloidal lignin nanoparticles

Photonic crystals are optical materials that are often fabricated by assembly of particles into periodically arranged structures. However, assembly of lignin nanoparticles has been limited due to lacking methods and incomplete understanding of the interparticle forces and packing mechanisms. Here we show a centrifugation-assisted fabrication of photonic crystals with rainbow structural colors emitted from the structure covering the entire visible spectrum. Our results show that centrifugation is crucial for the formation of lignin photonic crystals, because assembly of lignin nanoparticles without centrifugation assistance leads to the formation of stripe patterns rather than photonic crystals. We further prove that the functions of centrifugation are to classify lignin nanoparticles according to their particle size and produce monodispersed particle layers that display gradient colors from red to violet. The different layers of lignin nanoparticles were assembled in a way that created semi-closed packing structures, which gave rise to coherent scattering. The diameter of the lignin nanoparticles in each color layer is smaller than that predicted by a modified Bragg’s equation. In situ optical microscope images provided additional evidence on the importance of dynamic rearrangement of lignin nanoparticles during their assembly into semi-closed packing structures. The preparation of lignin nanoparticles combined with the methodology for their classification and assembly pave the way for sustainable photonic crystals.

A modified multi-exposure fusion method for laser measurement of specular surfaces

Line laser is widely used in structural light three-dimensional (3D) measurement of metal parts; however, the laser stripes are severely disturbed when measuring complex surfaces. In the process of laser plaSignal sent for page signal is not returning for this article, hence not possible to proceed. Please do the needful, also return the task only after solving the issue. ne calibration, the laser stripe will be damaged by the pattern on the calibration board; when measuring metal surfaces, the laser stripe will be exposed unevenly. Overexposed parts show highlights and artifacts, while underexposed stripes appear burrs, high noise, or even undetectable due to material absorption, which will greatly affect the accuracy of stripe center extraction. In this paper, a modified multi-exposure fusion (MMEF) method is proposed to improve the dynamic range of laser stripe images by enhancing underexposed regions and reducing saturation. The MMEF method uses a “smoothness” index and a “validity” index to give more weight to smooth, Gaussian-like laser stripe patterns and extract reliable modulation information. To evaluate the effectiveness of our method, the performance of the MMEF method is tested for laser plane calibration and metal surface reconstruction, and the high dynamic range (HDR) method, retrieval fusion (RF) method, and exposure fusion (EF) method are introduced for comparison. Measurement experimental results show that the MMEF method proposed in this paper improves the laser plane calibration accuracy by 86.0% and the 3D measurement accuracy of metal surface by 12.5%.

Effect of heterogeneous environmental conditions on labyrinthine vegetation patterns.

Self-organization is a ubiquitous phenomenon in Nature due to the permanent balance between injection and dissipation of energy. The wavelength selection process is the main issue of pattern formation. Stripe, hexagon, square, and labyrinthine patterns are observed in homogeneous conditions. In systems with heterogeneous conditions, a single wavelength is not the rule. Large-scale self-organization of vegetation in arid environments can be affected by heterogeneities, such as interannual precipitation fluctuations, fire occurrences, topographic variations, grazing, soil depth distribution, and soil-moisture islands. Here, we investigate theoretically the emergence and persistence of vegetation labyrinthine patterns in ecosystems under deterministic heterogeneous conditions. Based on a simple local vegetation model with a space-varying parameter, we show evidence of perfect and imperfect labyrinthine patterns, as well as disordered vegetation self-organization. The intensity level and the correlation of the heterogeneities control the regularity of the labyrinthine self-organization. The phase diagram and the transitions of the labyrinthine morphologies are described with the aid of their global spatial features. We also investigate the local spatial structure of labyrinths. Our theoretical findings qualitatively agree with satellite images data of arid ecosystems that show labyrinthinelike textures without a single wavelength.

CALCULATION AND EXPERIMENTAL STUDY OF THE STRESS-STRAIN STATE OF ELEMENTS OF TECHNOLOGICAL SYSTEMS WITH USING OF THE METHOD OF FINITE ELEMENTS AND HOLOGRAPHIC INTERFEROMETRY

The work describes computational and experimental studies of the stress-strain state of elements of technological systems. The distribution of movements of individual surfaces is determined on the example of vice-type adjustable machine tools. In the course of experimental studies, normal displacements are determined from the pattern of stripes on the hologram. The components of the displacement vector in the plane of the investigated surfaces are determined by scanning speckle interferograms. The obtained distributions of the displacement components were compared with the distributions determined by the finite element method. Satisfactory convergence of the results of numerical and experimental studies has been confirmed. The constructed calculation models can be used for further studies of the behavior of the housings of vice-type devices under the action of complex loads. The advantage of the developed version of the calculation-experimental method of studying the stress-strain state is its direct focus on the verification of the calculation model. The basic results are the results of experimental studies in the form of patterns of interference bands. These pictures describe the distribution of displacement fields of points on the surfaces of the bodies under study. With this picture, which was obtained on a natural object, the pictures of displacement fields, which were obtained during calculations with the application of the finite element method, are compared. Numerically calculated pictures are modified depending on the boundary conditions that are applied, as well as on the characteristics of the finite element models that are being built. In order to determine adequate boundary conditions and acceptable variants of finite-element models, the functional of the discrepancy of the displacement distribution fields obtained, on the one hand, numerically, and on the other - experimentally, is minimized. This construction of the calculation model verification algorithm demonstrated its efficiency and effectiveness. Keywords: stress-strain state; technological system; machine tool; finite element method; contact interaction

Pattern Formation by Electric-Field Quench in a Mott Crystal.

The control of the Mott phase is intertwined with the spatial reorganization of the electronic states. Out-of-equilibrium driving forces typically lead to electronic patterns that are absent at equilibrium, whose nature is however often elusive. Here, we unveil a nanoscale pattern formation in the Ca2RuO4 Mott insulator. We demonstrate how an applied electric field spatially reconstructs the insulating phase that, uniquely after switching off the electric field, exhibits nanoscale stripe domains. The stripe pattern has regions with inequivalent octahedral distortions that we directly observe through high-resolution scanning transmission electron microscopy. The nanotexture depends on the orientation of the electric field; it is nonvolatile and rewritable. We theoretically simulate the charge and orbital reconstruction induced by a quench dynamics of the applied electric field providing clear-cut mechanisms for the stripe phase formation. Our results open the path for the design of nonvolatile electronics based on voltage-controlled nanometric phases.

DNA vs. Morphology in Delineating Species Boundaries of Endemic Mongolian Eodorcadion Taxa (Coleoptera: Cerambycidae)

This paper provides the first DNA sequences and phylogenetic insight into the Central Asian genus Eodorcadion. We used four molecular markers (COI, CAD, ITS2, and Histone 3) and investigated COI genetic distances to verify phylogenetic position of closely related taxa endemic to Mongolia of the ‘Eodorcadion intermedium species-group’. Histone3 data are presented for the first time for Cerambycidae species. We also designed new PCR primers for better amplification of the Cerambycidae COI barcode region. Morphology of all targeted taxa was examined by means of scanning electron microscopy. Our study showed that while there were very few nucleotide differences among COI sequences of three closely related taxa, such that they shared one haplotype, two of them were grouped separately in the all-data tree, and all three were morphologically distinguishable. Conversely, there was a clear barcode gap between E. intermedium intermedium and all the remaining taxa, including E. intermedium kozlovi. Based on the phylogeny, they belong to two different species-groups; thus, E. kozlovi is herein restored to specific rank. Using Bayesian analysis, we contrasted the COI-based tree with the one supported by nuclear data and showed that COI-only data are not sufficient to resolve the phylogeny of the recently derived flightless groups such as Dorcadionini. We conclude that the Eodorcadion intermedium species-group is a polyphyletic species assemblage, established based on the pattern of the elytral stripes, which may be a case of parallel evolution driven by ecological adaptation.

Full-cycle data purification strategy for multi-type weld seam classification with few-shot learning

Weld seam type confirmation is a key part of intelligent integrated welding to cope with adjustable schemes varying with the seam morphology. However, existing works are mainly based on qualitative joint description (QJD) and machine learning classification (MLC), which entail high costs in balancing multiple given parameters, acquiring sufficient data and generalizing for new seam types. In this article, taking the advantages of few-shot learning, we propose a full-cycle data purification strategy (DPS) to identify seam types. First, five typical weld seams are mapped under three laser stripe patterns to acquire the raw samples. Then, a series of compliance processing algorithms are performed with reference to the target dataset to build a scenario dataset: purified weld seam stripe mapping (P-WSSM). With a few-shot learning pre-model, a positive weld seam classification result is obtained based on a small-volume dataset and analyze several critical factors. In addition, to compensate the application drawbacks caused by the wide randomness of low-volume datasets, compliance distance based on integrated grayscale co-occurrence matrix (I-GLCM) is introduced to quantitatively measure P-WSSM and the target dataset. Ultimately, experiments show that the dual-line stripe mapping achieves 85.4% recognition accuracy for 5-way 5-shot, which is a competitive multi-type weld seam classification via few-shot learning.

Non-ideal MHD growth of current interchange tearing modes at plasma edge and response to externally-imposed flow

Current interchange tearing modes (CITMs) have been proposed to explain an intermittent eruption of electric current toward a divertor at an edge region of a tokamak device. Extended magnetohydrodynamic (MHD) simulations combined with the Scrape-Off-Layer diffusion model, which has been developed by the authors [Miura et al., Phys. Plasmas 24, 092111 (2017)], are carried out in order to study the growth of a CITM under influences of two-fluid and gyro-viscous effects, or non-ideal MHD effects. Numerical simulations both with and without an externally imposed azimuthal flow show that the growth of a CITM is observed for a relatively small flow velocity, and that a CITM can be a candidate mechanism for the intermittent eruption of the current in a tokamak, whether the growth is under influences of non-ideal MHD effects or not. The growth can be suppressed when an externally imposed azimuthal flow is sufficiently large to cause a finite radial displacement because such a displacement prevents a transition from an interchange to a tearing mode that is the key process of a CITM. Furthermore, it is also found that a stripe pattern similar to so-called streamers is formed in the course of the CITM growth. The basic nature of this streamer-like structure is also presented.

Coefficients of Reaction‐Diffusion Processes Derived From Patterns in Rocks

AbstractSelf‐organizing diffusion‐reaction systems naturally form complex patterns under far‐from‐equilibrium conditions. A representative example is the rhythmic concentration pattern of Fe‐oxides in Zebra rocks; these patterns include reddish‐brown stripes, rounded rods, and elliptical spots. Similar patterns are observed in the banded iron formations, which are presumed to have formed in the early earth under global glaciation. We propose that such patterns can be used directly (e.g., by computer‐vision‐analysis) to infer basic quantities relevant to their formation giving information on generalized chemical gradients. Here we present a phase‐field model that quantitatively captures the distinct Zebra rock patterns based on the concept of phase separation that describes the process forming Liesegang stripes. We find that diffusion coefficients (the bulk self‐diffusivities of the native species and the mobility of the reaction product) play an essential role in controlling the appearance of regular stripe patterns as well as the transition from stripes to spots. The numerical results are carefully benchmarked with well‐established empirical spacing law, width law, timing law and the Matalon‐Packter law. Using this model, we invert for the important process parameters originating from the intrinsic material properties, the self‐diffusivity ratio and the mobility of Fe‐oxides with a series of Zebra rock samples. This study allows a quantitative prediction of the generalized chemical gradients in mineralized source rocks without intrusive measurements, providing a better intuition for the mineral exploration space.

Comparison of 3D Sensors for Automating Bolt-Tightening Operations in the Automotive Industry.

Machine vision systems are widely used in assembly lines for providing sensing abilities to robots to allow them to handle dynamic environments. This paper presents a comparison of 3D sensors for evaluating which one is best suited for usage in a machine vision system for robotic fastening operations within an automotive assembly line. The perception system is necessary for taking into account the position uncertainty that arises from the vehicles being transported in an aerial conveyor. Three sensors with different working principles were compared, namely laser triangulation (SICK TriSpector1030), structured light with sequential stripe patterns (Photoneo PhoXi S) and structured light with infrared speckle pattern (Asus Xtion Pro Live). The accuracy of the sensors was measured by computing the root mean square error (RMSE) of the point cloud registrations between their scans and two types of reference point clouds, namely, CAD files and 3D sensor scans. Overall, the RMSE was lower when using sensor scans, with the SICK TriSpector1030 achieving the best results (0.25 mm ± 0.03 mm), the Photoneo PhoXi S having the intermediate performance (0.49 mm ± 0.14 mm) and the Asus Xtion Pro Live obtaining the higher RMSE (1.01 mm ± 0.11 mm). Considering the use case requirements, the final machine vision system relied on the SICK TriSpector1030 sensor and was integrated with a collaborative robot, which was successfully deployed in an vehicle assembly line, achieving 94% success in 53,400 screwing operations.

Spatially extended dislocations produced by the dispersive Swift-Hohenberg equation.

Motivated by previous results showing that the addition of a linear dispersive term to the two-dimensional Kuramoto-Sivashinsky equationhas a dramatic effect on the pattern formation, we study the Swift-Hohenberg equationwith an added linear dispersive term, the dispersive Swift-Hohenberg equation(DSHE). The DSHE produces stripe patterns with spatially extended defects that we call seams. A seam is defined to be a dislocation that is smeared out along a line segment that is obliquely oriented relative to an axis of reflectional symmetry. In contrast to the dispersive Kuramoto-Sivashinsky equation, the DSHE has a narrow band of unstable wavelengths close to an instability threshold. This allows for analytical progress to be made. We show that the amplitude equationfor the DSHE close to threshold is a special case of the anisotropic complex Ginzburg-Landau equation(ACGLE) and that seams in the DSHE correspond to spiral waves in the ACGLE. Seam defects and the corresponding spiral waves tend to organize themselves into chains, and we obtain formulas for the velocity of the spiral wave cores and for the spacing between them. In the limit of strong dispersion, a perturbative analysis yields a relationship between the amplitude and wavelength of a stripe pattern and its propagation velocity. Numerical integrations of the ACGLE and the DSHE confirm these analytical results.

酸化スズナノ粒子サスペンションを用いたマイクロスケールのパターニング

This review focuses on our results on the fabrication of large-area patterning of tin oxide suspensions by the “micromolding in capillary” (MIMIC) method, one of the soft lithography techniques. Usually, suspensions with high solid loadings have been experimented, but since the filling mechanism of the MIMIC method is capillary action, the viscosity increases during the process, resulting in a smaller patterning area. We have confirmed that a low solids ethanol suspension of tin oxide nanoparticle can be used to achieve large-area patterning, forming a stripe pattern with a thickness of almost 1/3 the depth of the mold channel, resulting in a dense structure. Confirming the patterning mechanism, we found that controlling solvent evaporation during the process was very effective. It is expected that this MIMIC process for low solids loading suspensions of nanoparticles will be widely deployed for other types of ceramic suspensions.

Discovery of new Fe2Ni2CrAlx multi-principal element alloys with promising mechanical properties

Thermodynamic calculations were utilized to accelerate the pace of discovering promising composition combination by tailoring phase fraction. Then a family of Fe2Ni2CrAlx multi-principal element alloys (MPEAs) were synthesized to investigate the effect of Al on the crystal structure, microstructural evolution, and mechanical properties. A two-phase, face-centered cubic (FCC) and body-centered cubic (BCC), structure was identified in alloys with lower Al content (x = 0.9 and 1.1), the alloy consists of structure with stripe patterns. As the Al concentration increased, the FCC phases disappeared, the volume fraction of BCC and B2 phase increased. The morphology turned into polygonal grains in which the periodic maze-shaped microstructure can be identified. Higher Al content dramatically increased the nanohardness and strength of the Fe2Ni2CrAlx MPEAs, but reduced the plasticity. Among the developed alloys, the Fe2Ni2CrAl1.2 alloy displayed the best property combination, with yield stress, compressive strength, and plasticity of 1117.8 MPa, 2961 MPa and 42.3%. These values are superior to most reported as-cast MPEAs. Precipitation strengthening was found to be the main strengthening mechanism responsible for the enhanced mechanical properties of the Fe2Ni2CrAl1.2 alloy. The current work offers the systematic understanding of the strengthening.

Design and Implementation of Remote Controlling System Using GAN in Optical Camera Communication

This article illustrates the controlling mechanism along with data transmission using optical camera communication in both line-of-sight and non-line-of sight (NLOS) environment. The transmitter of the system is mainly composite of microcontroller (Arduino Mega), DHT sensor, two LEDs, and four push button switches. Here, two LEDs are continuously transmitting the control and data signal. The control signal is operated through push button switches. We have used four different control signals that are transmitted from the LEDs and data transmission by collecting data from the surrounding through the temperature and humidity sensor. The entire transmitter operations are processed and controlled through arduino programming in a microcontroller. The COOK modulation technique is used for this system. For data reception, we have used laptop's camera that is controlled through five different exposure times and operated based on the rolling shutter effect of the camera. A logistic regression algorithm is applied to recognize the data transmitting LED from the normalized intensity of the stripe patterns. The receiver is capable to collect data under certain conditions, if the light source is obstructed by an object through deep neural network. Again, Generative Adversial Network (GAN) is used as a decoder to reduce the BER during moving scenario and NLOS conditions. Different activation functions are used in the GAN model to find the optimum solution for the system. However, we have archived the maximum 2.5 m communication distance with 10-4 BER. The receiver program is designed using Python 3.8.