Arbitrary Shape Research Articles

A Numerical Approach to Modeling Electromagnetic Response of Dynamic Medium in Arbitrary Shape

In this letter, the electromagnetic (EM) response of a dynamic medium (moving or deforming) is modeled via a suggested method belonging to the class of matrix exponential (ME). Because of the dynamicity in addition to the inherent nonlinearity of the medium, the interaction between it and EM fields becomes much tangled compared to when the medium is stationary. Such a complication is accounted for by assigning the spacetime variation to EM parameters. Moreover, the possible explicit parameter nonlinearity is coped with in a forward time marching routine. Our method retains superiorities in simplicity, numerical stability, and generality. Two numerical tests pertaining, respectively, to the EM scattering of dynamic ferromagnetic block and cylinder are provided for confirming the validity and for exemplifying the application of the suggested method.

Fabrication of 3D hierarchical networks adsorbent immobilized MoS2 for adsorption of Ag(I) from aqueous solution

MoS2 as a nanomaterial, is popular in the field of water treatment due to the large specific surface area and abundant sulfur groups. However, the application of MoS2 as the powder absorbent is limited by the difficulty of separation and reuse in aqueous systems. Hence, we used the self-assembly characteristic of graphene oxide (GO) to immobilize MoS2 in three-dimensional (3D) reduced graphene oxide (rGO) system while loading inside melamine foam (MF) with 3D network structure by a one-step method, and then constructed sodium alginate (SA) cross-linked network by Ca2+ to fabricate a novel flexible, easy separable and structurally stable 3D hierarchical networks adsorbent (SA@MoS2/rGO/MF). The SA@MoS2/rGO/MF was applied for adsorption of Ag(I) in aqueous solution, and the maximum adsorption capacity was 1012.51 mg/g. The SA@MoS2/rGO/MF as a promising adsorbent could be used in the treatment of wastewater containing high concentration Ag(I). Interesting, the redox reaction and coordination reaction occurred simultaneously during the adsorption process to generate silver elemental and Ag2S, which are valuable sources for application in other fields. It’s worth noting that the SA@MoS2/rGO/MF could be constructed into arbitrary shape in favor of mass production. This work provides a feasible strategy for the separation of powder adsorbents.

Programmable Shaping of Femtosecond Pulses Using a One-Dimensional Photonic Crystal with Continuous Spatial Modulation of the Refractive Index

An algorithm for constructing the structure of a one-dimensional photonic crystal, which forms a femtosecond pulse of an arbitrary given shape when reflecting a Gaussian pulse, is developed theoretically. The method is illustrated by the example of a rectangular pulse. Examples for simple pulse shapes are given, the influence of optical absorption is evaluated, and a method for its compensation is proposed.

Simulation of Tthe Amplitude of Transverse Oscillations of the Rod System upon Impact of a Falling Load, Taking into account Deformation in the Contact Area

The oscillatory process of a rod system of arbitrary shape under shock interaction with a falling load is considered. The system may consist of a large number of rods connected to each other rigidly or pivotally, and striking is assumed to be one of the core elements, thus causing a complex oscillatory process. As an example, vibrations of a rigidly sealed statically indeterminate flat two-post frame experiencing a drop of a load of a given mass and pre-impact velocity are simulated. One of the vertical pillars of the frame has an initial curvature, the presence of which affects the maximum amplitude of transverse vibrations arising from impact. The impact of the load on the frame crossbar is modeled taking into account the deformation in the contact area, which is justified from the point of view of the accuracy of the calculations, because otherwise the magnitude of the impact force will be overestimated. When modeling the impact interaction of the load and the rod system under consideration, it is assumed that the falling load has the shape of a cylinder with a certain length of the generatrix. Linearization of the relationship between force and deformation of cylindrical surfaces is used. The proposed method of modeling the amplitude of transverse oscillations makes it possible to further study the characteristics of the oscillatory process depending on the mass of the falling load and its pre-impact velocity, as well as on the configuration of the rod system. The relevance of the work for calculations of structural elements of various purposes experiencing impact is emphasized, since the presented model can be used for engineering calculations of a wide class of core systems.

In Ukrainian

Investigating the formation of inversion layers (IL) at the Si-SiO2 interface in the manufacturing technology of silicon photodetectors, some dynamics of dislocations after isothermal annealing were revealed, which were absent in samples without inversion. After selective etching of samples with inversion layers, localization of dislocations on the periphery of responsive elements (RE) with accumulation of guard rings (GR) or other elements of n+-type topology outside the RE was observed. This testified to the movement of dislocations on the surface of the Si-SiO2 structures with IL in the direction of the periphery of the crystal during isothermal annealing, which contributed to a significant decrease in the density of structural defects in RE. The described phenomenon can be used to obtain highly doped defect-free silicon structures. Since the presence of dislocations or other violations of the crystal lattice negatively affect the parameters of the products. In the case of using the described phenomenon as a technological method of “cleaning” the surface of silicon structures, there is a need for controlled formation of IL. One of the methods of forming inversion layers can be thermal oxidation in hydrochloric acid vapors according to the principle of dry-wet-dry oxidation (for p-type silicon). Another method that does not require additional materials is the annealing of Si-SiO2 structures at a temperature of 900–950 Celsium degrees in a nitrogen atmosphere for ≥ 240 minutes. Inversion channels, in this case, will be formed due to the redistribution and diffusion of metal impurities in the oxide (which were introduced during previous thermal operations) to the Si-SiO2 interface. In the described case, these structural defects after annealing were localized in the GR, which is also an active element of the phododiodes, as it limits the dark current of the RE, accordingly, the dark current of the GR should also be low. To be able to implement this method, it is necessary to create passive n+-regions on the periphery of the crystals, limited by oxide, which will be the locations of defects after annealing. It can be both separate areas of arbitrary shape and a concentric ring outside the GR. Elements that will be the locations of defects on the periphery can be cut off at the stage of separating the substrates into crystals. After annealing, it is necessary to remove the IL and form an anti-reflective coating by any known method, since the presence of inversion channels contributes to the growth of dark currents. When examining the morphology of defect localization areas after annealing under high-magnification microscopes and with the help of an atomic force microscope, the formation of hexagonal and round defects, which are partial marginal Frank dislocation loops, was observed. The mechanism of dislocation movement described in this article has not been thoroughly studied by us and requires additional research, but it may be related to Cottrell atmospheres and their interaction with IL

Text kernel calculation for arbitrary shape text detection

Text kernel calculation for arbitrary shape text detection

Efficient Pyrolysis Model for Large Biomass Particles with Arbitrary Shapes Based on a Composed-Sphere Concept and Voronoi Tessellation

Efficient Pyrolysis Model for Large Biomass Particles with Arbitrary Shapes Based on a Composed-Sphere Concept and Voronoi Tessellation

Super-efficient Echocardiography Video Segmentation via Proxy- and Kernel-Based Semi-supervised Learning

Automatic segmentation of left ventricular endocardium in echocardiography videos is critical for assessing various cardiac functions and improving the diagnosis of cardiac diseases. It is yet a challenging task due to heavy speckle noise, significant shape variability of cardiac structure, and limited labeled data. Particularly, the real-time demand in clinical practice makes this task even harder. In this paper, we propose a novel proxy- and kernel-based semi-supervised segmentation network (PKEcho-Net) to comprehensively address these challenges. We first propose a multi-scale region proxy (MRP) mechanism to model the region-wise contexts, in which a learnable region proxy with an arbitrary shape is developed in each layer of the encoder, allowing the network to identify homogeneous semantics and hence alleviate the influence of speckle noise on segmentation. To sufficiently and efficiently exploit temporal consistency, different from traditional methods which only utilize the temporal contexts of two neighboring frames via feature warping or self-attention mechanism, we formulate the semi-supervised segmentation with a group of learnable kernels, which can naturally and uniformly encode the appearances of left ventricular endocardium, as well as extracting the inter-frame contexts across the whole video to resist the fast shape variability of cardiac structures. Extensive experiments have been conducted on two famous public echocardiography video datasets, EchoNet-Dynamic and CAMUS. Our model achieves the best performance-efficiency trade-off when compared with other state-of-the-art approaches, attaining comparative accuracy with a much faster speed. The code is available at https://github.com/JingyinLin/PKEcho-Net.

Learning Continuous Depth Representation via Geometric Spatial Aggregator

Depth map super-resolution (DSR) has been a fundamental task for 3D computer vision. While arbitrary scale DSR is a more realistic setting in this scenario, previous approaches predominantly suffer from the issue of inefficient real-numbered scale upsampling. To explicitly address this issue, we propose a novel continuous depth representation for DSR. The heart of this representation is our proposed Geometric Spatial Aggregator (GSA), which exploits a distance field modulated by arbitrarily upsampled target gridding, through which the geometric information is explicitly introduced into feature aggregation and target generation. Furthermore, bricking with GSA, we present a transformer-style backbone named GeoDSR, which possesses a principled way to construct the functional mapping between local coordinates and the high-resolution output results, empowering our model with the advantage of arbitrary shape transformation ready to help diverse zooming demand. Extensive experimental results on standard depth map benchmarks, e.g., NYU v2, have demonstrated that the proposed framework achieves significant restoration gain in arbitrary scale depth map super-resolution compared with the prior art. Our codes are available at https://github.com/nana01219/GeoDSR.

Thermal conductivity effect on thermophoresis of charged spheroidal colloids in aqueous media.

Thermophoresis of spheroidal colloids in aqueous media under the thermal conductivity effect is analyzed. The thermophoretic velocity and the thermodiffusion coefficient of spheroidal colloids have been formulated for extremely thin electric double layer (EDL) cases. Furthermore, a numerical thermophoretic model is built for arbitrary EDL thickness cases. The parametric studies show that the thermal conductivity mismatch of particle and liquid gives rise to a nonlinear temperature region around the spheroid, with the thickness close to the minor semiaxis. When the EDL region is thin relative to such nonlinear temperature region, the thermal conductivity effect on the thermophoresis of spheroidal colloids is significant, which strongly depends on the ratio of the minor semiaxis to the EDL thickness, the thermal conductivity ratio of particle to liquid, and the particle aspect ratio. Finally, to estimate the thermodiffusion coefficient of spheroidal colloids with arbitrary thermal conductivity, electrolyte concentration, and particle shape, the average dimensionless axial temperature gradient on the spheroidal equator plane in the EDL region is proposed.

A physically consistent Discrete Element Method for arbitrary shapes using Volume-interacting Level Sets

The properties of granular materials depend strongly on the shapes of their individual constituent particles or granules. Nonetheless, incorporating the effects of non-spherical or complex particle shapes into existing modelling frameworks, such as the discrete element method (DEM), has remained challenging. In this work, we propose the volume-interaction level set DEM (VLS-DEM) approach for carrying out physically accurate simulations of particles with arbitrary geometries. VLS-DEM builds upon level set DEM (LS-DEM), both of which implicitly define the geometry of a particle through a discrete signed distance function. However, instead of using surface nodes to compute the interparticle forces, VLS-DEM uses the overlap volume as computed by an Octree integration algorithm. This addresses some of the shortcomings of LS-DEM in terms of the accuracy and precision of the shape description and opens up the possibility for bottom-up parametrisation methods. A number of tests were performed to compare VLS-DEM with regular DEM, LS-DEM, and analytical models. VLS-DEM is shown to give physically accurate results, comparable to analytical theory, even for highly complex systems such as those with concave interlocked particles.

Modelling of gas-solid heat transfer and pressure drop in a rock-packed bed using pore-scale simulations

The aim of this work is to provide closure laws for a macroscopic model of the heat and momentum transfer of real rock packings. We use X-ray nanotomography to obtain the geometry of two real rock packings (basalt and gravel). To address preferential flow paths on non-periodic REV, we have developed a method to properly extract closure laws on non-periodic REV from thermally fully developed pore-scale flow simulations. Several pore-scale simulations are performed over a range of Reynolds numbers (5–243) with a Prandtl number of 0.7. Then there are proposals for closure laws for real rocks, which are of completely arbitrary shape. These laws are based on a Nusselt number correlation and a dimensionless drag force correlation extracted from the pore scale simulations. The Nusselt number correlation is an extension for arbitrary shapes, i.e. real rocks, of the one proposed by Sun et al. (2015). The dimensionless drag force correlation is an original expression in excellent agreement with the experimental datas of Allen et al. (2013). The results support the hypothesis that the mean Sauter diameter is a key parameter that captures the similar behaviour of real rock packings, either for heat or momentum transfer. As this parameter cannot be replaced by other characteristic lengths in the closure laws, it needs to be properly evaluated, for example using nanotomography. For optimising the design of real rock-packed beds, the proposed closure laws allow accurate upscaling of heat transfer and pressure losses.

Universal optical polarizability for plasmonic nanostructures

Optical spectra of small metal nanoparticles are dominated by surface plasmon resonance. In this Letter, a simple analytical model for optical polarizability of metal nanoparticles of arbitrary shape is presented.

Silicon electrodeposition from the KF-KCl-K<sub>2</sub>SiF<sub>6</sub> and KF-KCl-KI-K<sub>2</sub>SiF<sub>6</sub> melts

Silicon and silicon-based materials find extensive applications in metallurgy, microelectronics, and other emerging industries. The field of use of synthesized silicon varies based on its morphology and purity. This study employs voltammetry, galvanostatic electrolysis, and scanning electron microscopy to examine the impact of KI surfactant (in mol %) to 66.5KF–33.3KCl–0.23K2SiF6 melt at 750°C on the electrowinning kinetics of silicon ions and the morphology of silicon deposits formed on a glassy carbon electrode. The findings demonstrate that the addition of potassium iodide to the KF–KCl–K2SiF6 melt at a concentration of 2 mol % induces changes in interfacial tension at the boundary between the glassy carbon, melt, and atmosphere. Consequently, the wetting of the glassy carbon with the melt decreases, leading to a reduction in the actual working surface area and, consequently, a decrease in cathode current while maintaining current density. Taking into account this effect and employing an algebraic estimation of the influence of the melt meniscus shape, it is postulated that the addition of KI does not significantly affect the kinetics of the cathode process. Nevertheless, the impact of KI addition on the morphology of electrodeposited silicon is mentioned. During the electrolysis of the KF–KCl–K2SiF6 melt, fibrous silicon deposits with arbitrary shapes are formed on the glassy carbon electrode, whereas the addition of 2 and 4 mol % of potassium iodide to the melt leads to the agglomeration and smoothing of silicon deposits under the same electrolysis conditions (cathode current density: 0.02 A/cm2, electrolysis duration: 2 h). The obtained results indicate the potential to manipulate the morphology of electrodeposited silicon for specific applications in various fields.

A New Method for Analyzing Dynamic Characteristics of Generalized Planar Frame Structures Under Complex Conditions

This paper presents a novel method for analyzing the vibration characteristics of planar frame structure composed of straight beams with arbitrary shapes. The method is based on the first-order shear theory, which takes into account the shear deformation and cross-sectional rotational inertia of the beams. On the one hand, an improved Fourier series method (IFSM) is employed to approximate the displacement function of the straight beam, and the displacements are determined by using the Rayleigh–Ritz method. On the other hand, the displacements of the curved beam are obtained by using the finite element method (FEM), which are then combined with the IFSM for the analysis of coupled nodes of straight and curved beams. This results in a computational method for calculating the vibration characteristics of complex planar frame structures with concentrated masses, straight and curved beams, arbitrary boundary conditions, and any connection form of nodes. The applicability of the proposed method is demonstrated through numerical examples, including planar frame structure with arbitrary shapes composed of straight beams, different cross-sectional shapes, and combinations of beam with various cross-sectional shapes, as well as planar frame structures with straight and curved beams. The results of the proposed method are validated by comparing them with those obtained from literature or finite element software ABAQUS. The numerical examples show that the proposed method combining the IFSM with FEM has the advantages of high accuracy, good convergence, and strong applicability for calculating the vibration characteristics of planar frame structures.

Thermal-hydraulic-mechanical analysis of enhanced geothermal reservoirs with hybrid fracture patterns using a combined XFEM and EDFM-MINC model

The long-term fluid circulation of Enhanced Geothermal Systems (EGS) involves complex coupled Thermal-Hydrological-Mechanical (THM) processes dominated by both hydraulic and activated natural fractures. The simulation of such multiphysical processes is known to be a challenging problem. In this work, we have developed an integrated numerical approach to advance the multiphysical simulation of EGS. In our model, the hydraulic fractures of arbitrary shapes in response to pressure changes and thermal strains are handled by the three-dimensional (3D) eXtended Finite Element Method (XFEM). The induced/natural fractures are incorporated into the model and treated as one continuum of the Multiple INteracting Continua (MINC) for the investigation of their impacts. A TOUGH -based program, TOUGH2-EGS, is utilized to simulate the Thermal-Hydrological processes. The 3D Embedded Discrete Fracture Method (EDFM), compatible with the 3D XFEM, is adopted to model the hydraulic fractures. Sensitivity analyses are performed for this model in terms of injection temperature and thermal expansivity. The hybrid EDFM and MINC model is established and analyzed for an EGS with both hydraulic and induced/natural fractures. The convergence performance of the single-fracture model shows that an appropriate stiffness coefficient is essential for this model and different choices of the coefficient values result in distinct behaviors. Our numerical results illustrate that the fracture aperture is opened by the cold fluid injection and the reservoir performance is dominated by the thermal stress/strain, which highlights the necessity of multiphysical simulation. In the hybrid model, the enhancement of the natural fracture permeability notably delays the thermal breakthrough by allowing injected fluid to contact more hot reservoirs. The novelties of this work lie in three aspects. Firstly, the combined 3D XFEM and EDFM is capable of handling arbitrary fracture shapes in a 3D EGS model. Secondly, the hybrid hydraulic and induced/natural fracture model enables us to establish the stimulated reservoir volume of the EGS and investigate the operational and geological parameters. Thirdly, the introduction of fracture stiffness stabilizes the numerical solution.

A coupled approach to predict cone-cracks in spherical indentation tests with smooth or rough indenters

Indentation tests are largely exploited in experiments to characterize the mechanical and fracture properties of the materials from the resulting crack patterns. This work proposes an efficient theoretical and computational framework, whose implementation is detailed for 2D axisymmetric and for 3D geometries, to simulate indentation-induced cracking phenomena caused by non-conforming contacts with indenter profiles of an arbitrary shape. The formulation hinges on the coupling of the MPJR (eMbedded Profile for Joint Roughness) interface finite elements which embed the indenter profile to efficiently solve the contact problem between non-planar bodies, and the phase-field model for brittle fracture to simulate crack evolution and nonlocal damage in the substrate. The novel framework is applied to predict cone-crack formation in the case of indentation tests with smooth spherical indenters, with validation against experimental data. Then, the methodology is employed for the very first time in the literature to assess the effect of surface roughness superimposed on the shape of the smooth spherical indenter. In terms of physical insights, numerical predictions quantify the dependencies of the critical load for crack nucleation and the crack radius on the amplitude of roughness in comparison with the behavior of smooth indenters. Again, the consistency with available experimental trends is noticed.

Epicycle-model-guided arbitrary shaped customization of structured light

Structured light has been exploited as an important tool for particle manipulation along a desired complex path. However, generating the required structured light illumination for the creation of an arbitrary shape without an analytic expression as a guide is challenging, specifically for designing a structured beam by mapping the shape of an arbitrary object. To address this issue, we propose an effective scheme to customize structured light freely and precisely by modifying the epicycle model in astrophysics. Predesigned structured beams can be identified with or without explicit analytic expressions of the desired shapes. Moreover, we study the roles and relationships between the number of epicycles and the number of key points. The local stretching and transformation of a specific structured beam are also analyzed. The advantages of the proposed method are demonstrated by conducting dynamic manipulation experiments using polystyrene particles. This method is simple and intuitive and provides an effective toolkit for the design of structured light for more complex tasks, thus facilitating advanced applications in optical manipulations.

A Comprehensive Review of DNA Origami Stabilization Techniques

In recent years, DNA has emerged as a powerful tool in the field of nanotechnology. The DNA origami technique is largely responsible for this, revolutionizing nanofabrication due to its controllability, precision, and ability to leverage DNA’s unique properties. The technique consists of folding a long, single-stranded DNA (called a scaffold strand) by binding it with shorter staple strands to create almost any shape desired. With a desired structure in mind, researchers can design and assemble scaffold and staple strands using computer software like Cadnano or Tiamat. This is possible because of the Watson-Crick base pairing of DNA strands, which allows for programmable self-assembly of DNA nanostructures and therefore, the synthesis of arbitrary 2D and 3D shapes. Because DNA is a biomolecule,the nanostructures are also biocompatible and can be employed in biological applications including drug delivery. DNA origami nanostructures are not only limited to biological applications; they have also found uses in nanophotonics, plasmonics, and electronics. However, DNA origami still faces many challenges before it can be widely adopted. One such challenge is ensuring stability, and thus guaranteeing the performance of the DNA origami, in the presence of heat, nuclease in organic bodies, and chaotropic agents. This warrants the question: what methodologies can be employed to best stabilize DNA origami structures? This paper further focuses on two methods: covalently binding various molecules by cross-linking and non-binding encapsulation. Detailed analysis and comparison between various molecules used to bind and coat DNA nanostructures is used to evaluate performance and applicability of each method. In the end an oligolysines coating cross-linked with glutaraldehyde was found to have the strongest biological stability, thymine cross-linking had the strongest thermal stability, a silica coating had the best stability against the largest number of factors, and both graphene and Al3O2 coatings had the best mechanical stability.

A density connection weight-based clustering approach for dataset with density-sparse region

Density-Based clustering, an important clustering analysis approach, has several advantages of discovering clusters with arbitrary shapes and identifying noise samples etc. However, existing density-based clustering approaches cannot effectively identify clusters in density-sparse region. In this paper, we propose a density-based clustering approach for dataset with density-sparse region by using density connection weight. Firstly, we define a series of new concepts, such as density connection weight and average weight. And data objects are divided into core objects, boundary objects and noise objects according to average weight, which can effectively distinguish core objects and boundary objects in density-sparse region. Secondly, a density clustering assignment strategy is constructed based on density connection weight. A density clustering algorithm, together with the dimensionality reduction using t-SNE, judiciously handles the low-density clusters in multi-density datasets and the minimal clusters in extremely imbalanced datasets. In the end, the experimental results on the UCI and synthetic datasets validate that our algorithm exhibits prominent clustering performance, especially while being adapted in diverse clustering tasks, including the multi-density, imbalanced and uniform distribution datasets.