Arbitrary Shape Research Articles

Capillary flow in corners slowed down by gravity and evaporation

Abstract Capillary flow in corner geometries in the presence of gravity and evaporation is relevant for numerous natural phenomena and industrial applications. In the absence of gravity, the length of the rivulet in the corner follows the t 1/2 asymptotic law (Lucas-Washburn kinetics), where t is the time. If the liquid flows against gravity, the propagation of the rivulet tip decelerates to follow the t 1/3 asymptotic law. In this paper, we present a model for simulation of the rivulet shape evolution in a corner with an arbitrary cross-section shape. Gravity and evaporation are taken into account. Several exact and asymptotic solutions are presented. In particular, a simple expression for the proportionality coefficient in the t 1/3 asymptotic law is derived, as well as an expression for the cross-over time moment corresponding to change from the t 1/2 to t 1/3 asymptotic behavior. In the presence of evaporation, the rivulet length reaches a maximal value, at which the rate of evaporation is balanced by the rate of the capillary flow. We derive expressions for the maximal rivulet length in the limiting cases of “strong” and “weak” evaporation. In the case of “strong” evaporation, the maximal rivulet length behaves as E −1/2, where E denotes the dimensionless evaporation rate. In the case of “weak” evaporation, uniform evaporation rate and triangular groove geometry, the maximal rivulet length is proportional to E −1/5 Bo −3/5, where Bo denotes the Bond number.

Lightweight and efficient beam-shaping metalens for converting Gaussian beams into 2D flat-top beams

Flat-top laser beams have significant applications in fields such as laser processing due to their uniform intensity distribution and clear boundaries. Since lasers typically emit Gaussian beams in the fundamental mode, devices that convert Gaussian beams into flat-top beams are essential. However, traditional beam shapers composed of refractive or diffractive optical elements need improvements in volume, weight, and cost. In this study, we propose a beam-shaping metalens to address these issues. We present an extended Gerchberg-Saxton (GS) algorithm to design two beam-shaping metalenses that convert Gaussian beams into 2D circular and square flat-top beams, respectively. We develop an analytical rapid simulation (ARS) method for simulating metalenses and verify its accuracy. Additionally, we consider the microloading effect in etching and compensate for the impact caused by etching depth inconsistencies. We experimentally fabricated and characterized two beam-shaping metalenses, achieving a circular flat-top beam with a conversion efficiency of 91.8% and an RMS value of 16.7%, and a square flat-top beam with a conversion efficiency of 89.7% and an RMS value of 24.0%. This method for designing beam-shaping metalenses that convert Gaussian beams into flat-top beams of arbitrary shapes provides a novel solution for laser beam shaping.

High efficiency focusing vortex generation and multichannel multiplexing based on terahertz metasurfaces

Single-function metasurfaces can only perform one task and thus cannot satisfy the demands of many advanced applications. Employing multifunctional and multiplexing metasurfaces considerably increases the integration density of functional devices. Therefore, orbital angular momentum (OAM) multiplexing metasurfaces have been designed to increase transmission capacity. In this study, a bilayer Pancharatnam–Berry phase unit cell operating at two frequencies in the terahertz (THz) band is proposed. The unit cell has a sub-wavelength thickness that can be used as a functional element for constructing ultrathin and compact metasurfaces for wavefront manipulation. Cross-polarization conversion ratio of 86.3% and 88.5% are obtained at the two frequencies, respectively. We design three multifunction metasurfaces to verify the method. First, two vortex metalenses are designed to focus vortex beams in the sub-wavelength scale at various frequencies. Furthermore, multichannel OAMs with various modes and arbitrary shape of OAM beam arrays can be realized using segmented metasurfaces. Finally, multichannel OAM multiplexing with the frequency selection and polarization dependence were simultaneously realized on a metasurface. Such metasurfaces can be used to realize large-capacity and high-spectrum-efficiency OAM communication. This paper contributes to the disciplines of photonic integration, multiplexing, and multifunctional metasurfaces.

Study on simplified calculation method for lateral natural frequency of water within U-shaped aqueducts

The water sloshing in aqueducts under seismic excitations is essentially a sloshing problem of water in liquid storage tanks. However, the present calculation method for the lateral natural frequency of water within U-shaped aqueducts is extremely complicated, inefficient, and only valid for the first lateral natural frequency calculation. Based on an existing calculation method derived from the Rayleigh quotient for the natural frequency of water in 2D (two-dimensional) containers with arbitrary shapes, a simplified calculation method for the lateral natural frequency of water within U-shaped aqueducts is proposed. The Taylor series, along with the β and Γ functions, is used to simplify the complex non-elementary integrals as algebraic expressions, making this calculation method convenient and efficient enough to calculate the first four lateral natural frequency of water in U-shaped aqueducts. Furthermore, a numerical model established by OpenFOAM-9 is employed to validate the accuracy of the proposed method. Validation shows the proposed calculation method is 9 times as precise as the method specified in Chinese code for the first lateral natural frequency calculation, and it can also calculate the second- to fourth-order lateral frequencies of the water in U-shaped aqueducts precisely. Results also show when water level inside the U-shaped aqueduct is beyond the semicircle part, aqueduct width significantly influences water natural frequency, whereas water depth has a minor impact.

DiaDet-R: A lightweight and accurate rotated detector for diatom detection in drowning diagnostics

DiaDet-R: A lightweight and accurate rotated detector for diatom detection in drowning diagnostics

Static continuous bulk material model for inclined bunker section

Purpose. Obtaining an analytical pattern of pressure distribution of bulk material based on the classical Jansen’s model for an inclined outlet part of a hopper with an arbitrary cross-sectional shape. Methodology. The work used a set of research methods, including scientific analysis and synthesis of available technical information regarding the current regulatory and professional approaches to determining the pressure from bulk material in container structures. Computer modeling methods based on the numerical method of structural mechanics ‒ the finite element method ‒ were also used. Analysis of the performance of structural options was carried out using the SCAD design and computing complex (Ukraine). A separate direction in the work was design developments, which included methods for engineering assessment of the accuracy and reliability of the results obtained. Findings. An analytical expression for determining the vertical pressure of bulk material is obtained, which reflects in a closed form the regularities of its distribution for the case of a straight inclined rigid wall of the outlet part of the hopper container with an arbitrary cross-sectional shape. The pressure value of the bulk material according to this expression quantitatively exceeds the pressure value according to known analytical models. This gives grounds to believe that when loading the hopper structures, a change in the structure of the bulk material occurs, which is described in the literature as its loosening. Originality. The conducted researches allowed for the first time to establish the regularities of the pressure distribution of bulk material during static operation of a hopper structure with straight inclined walls. The obtained expression is structurally the product of two power functions, in which the exponent is the expressions that reproduce the geometry of the outlet part of the hopper structure and the material of its side walls. Practical value. The obtained expression allows to calculate the vertical and, if necessary, normal pressure of bulk material for straight inclined walls of hopper structures. It is proved that the pressure increases significantly with increasing its depth, which in the case of unloading the container should lead to the destruction of the static form of laying of bulk material. The developed model is the basis for a more detailed consideration of the characteristics of bulk material, such as the density of laying or the angle of laying.

A spheroidal dielectric compressible liquid inclusion in an infinite transversely isotropic piezoelectric matrix

We examine the three-dimensional problem associated with a spheroidal dielectric compressible liquid inclusion perfectly bonded to an infinite transversely isotropic piezoelectric matrix subjected to a uniform axisymmetric electromechanical loading at infinity. Our solution method is based on the general solution developed by [L. Kogan, C. Y. Hui and V. Molkov. Stress and induction field of a spheroidal inclusion or a penny-shaped crack in a transversely isotropic piezoelectric material. International Journal of Solids and Structures 33(19), pp. 2719–2737, 1996] describing the electroelastic field in a transversely isotropic piezoelectric solid. Specifically, the original boundary value problem is reduced to a set of four coupled linear algebraic equations. The internal uniform hydrostatic stress field within the liquid inclusion and the electroelastic field of displacements, electric potential, stresses and electric displacements in the piezoelectric matrix are then completely determined via the solution of this set of linear algebraic equations. A three-dimensional neutral liquid inclusion of arbitrary shape that does not disturb the prescribed uniform hydrostatic stresses and electric displacements in a generally anisotropic piezoelectric matrix is achieved.

Nonreciprocal chirality conversion in spatiotemporal evolutions of nematic colloidal entanglement.

In soft matter systems, there is a wealth of topological phenomena, such as singular disclination lines and nonsingular defects of skyrmions and hopfions. In a liquid crystal (LC), the topological nature of disclination lines and colloids induces chiral colloidal entanglements. How the chirality of the entanglements is deterministically created and how the chirality conversion is actuated in the disclinations with Möbius strip topology have never been explored. Here, we create colloidal entanglements with designed chirality in the nematic disclination loops with Möbius topology. An irreversible process of chirality change is revealed if we move the colloidal entanglement along the loops. A nonreciprocal chirality conversion in the dynamical colloidal entanglements is demonstrated, which is induced by the interplay between topological profiles and the geometrical curvature of the disclination loop. Colloidal entanglements in opposite chirality are templated in arbitrary shapes of disclination lines. This work opens opportunities to design smart colloidal materials.

Integrated anti-electronics for positron annihilation spectroscopy

Imaging the features of a sample using Positron Annihilation Spectroscopy (PAS) is currently achieved by rastering, i.e. by scanning the sample surface with a sharply focused positron beam. However, a beam of arbitrary shape (sculpted beam) would allow the application of more versatile single-pixel imaging (SPI) techniques. I introduce the design of a microelectronic device employing a 2D array of Zener diodes as an active positron moderator, capable of sculpting positron beams with resolution. The re-emitted positrons are accelerated towards the sample through a miniaturized electrostatic lens system and reaching resolution. The fast switch-on () and switch-off () time of the device would enable state-of-the-art positron annihilation lifetime spectroscopy (PALS) and PAS imaging with high spatial and temporal resolution.

High-accuracy iterative 6DoF pose tracking for large-size cabin assembly

Abstract Large-size cabin assembly is a challenging and labor-intensive task, while visual pose estimation of the cabin could enhance its efficiency and precision. The existing frameworks are mainly based on ellipse detection and projection calculation, leading to a limitation of accuracy and generalization. In this paper, we introduce a novel framework for pose tracking of large-size cabins based on iterative optimization of manipulation points to reduce the impact caused by 6DoF pose coupling, where four manipulation points iteratively transform the docking surface contour and align it with captured image. The method is applicable to arbitrary shapes of cabin docking surface and also extended to multiple perspectives. Both actual cabin assembly experiments and simulation experiments are performed, the results demonstrate that the proposed method is more accurate and robust than conventional methods.

Adaptative two-phase thermal circulation system for complex-shaped electronic device cooling

Thermal management using a vapor-liquid two-phase circulation system is challenging in compact and complex-shaped electronic devices. In this study, we design and fabricate a heat pipe that can adapt to various shapes, regardless of space constraints. The heat pipe is capable of bending or twisting in three dimensions, making it suitable for electronic devices of arbitrary shapes. It effectively transfers heat from in-plane chips to out-of-plane spaces through flexible circulation pathways. This two-phase heat cycle system achieves an ultra-high thermal conductivity of up to 11,363 W/m·K. The flexible and adaptive design strategy enables efficient heat transfer in complex and compact environments.

SynMARSS-An End-To-End Platform for the Parametric Generation of Synthetic InVivo Magnetic Resonance Spectra.

Synthetic magnetic resonance spectra (MRS) are mathematically generated spectra which can be used to investigate the assumptions of data analysis strategies, optimize experimental design, and as training data for the development and validation of machine learning tools. In this work, we extend Magnetic Resonance Spectrum Simulator (MARSS), a popular MRS basis set simulation tool, to be able to generate synthetic spectra for an arbitrary MRS sequence. The extension, referred to as synMARSS, converts a basis set as well as a set of NMR, tissue-related and additional sequence parameters into high-quality synthetic spectra via a parametric model. synMARSS is highly versatile, incorporating T1 and T2 relaxation, arbitrary line shape distortions and diffusion, while also quickly generating the large amount of training data needed for machine learning applications. Additionally, we extend MARSS to non-1H nuclei, such as 2H, 13C, and 31P. We use synthetic spectra to investigate the effects of approximating 14N heteronuclear coupling as weak homonuclear coupling, which was found to have small effects on the quantified concentrations for major metabolites for the implementation of PRESS at short echo time, but these effects increased at longer echo times.

A fully resolved SPH-DEM for simulation of debris flows with arbitrary particle shapes impacting flexible barriers

A fully resolved SPH-DEM for simulation of debris flows with arbitrary particle shapes impacting flexible barriers

Layer-Based Simulation for Three-Dimensional Fluid Flow in Spherical Coordinates.

Fluid flows in spherical coordinates have raised the interest of the graphics community in recent years. The majority of existing works focus on 2D manifold flows on a spherical shell, and there are still many unresolved problems for 3D simulations in spherical coordinates, such as boundary conditions for arbitrary obstacles and flexible artistic controls. In this article, we propose a practical spherical-coordinate simulator for flow motions in 3D domains. Based on a layer-by-layer structure and a boundary-aware pressure solving scheme, we are able to recover horizontal and vertical flow motions in the presence of arbitrary terrain shapes within a spherical shell of finite thickness. Our proposed method straightforwardly builds on the conventions of previous 2D-manifold spherical-coordinate simulations and provides flexible artistic control strategies for art design.

Piezoelectric transducer-assisted mass normalization of mode shapes in thin-walled structures

This paper introduces a robust and accurate, yet simple and straightforward technique for measuring mass-normalization scale factor for each vibration mode of thin-walled structures using a piezoelectric transducer. The methodology relies on electromechanical impedance measurement and the charge frequency response function of a piezoelectric transducer attached to the structure which leads to the determination of the mass-normalized component of mode shape at the force location i.e. reference point. The scaling factor for each vibration mode is determined by comparing the arbitrary mode shape with the mass-normalized one at the reference point.

Light-driven dancing of nematic colloids in fractional skyrmions and bimerons

Materials with full and fractional skyrmions are important for fundamental studies and can be applied as information carriers for applications in spintronics or skyrmionics. However, creation, direct optical observation and manipulation of different skyrmion textures remain challenging. Besides, how the transformation of skyrmion textures directs the dynamics of colloids is not well understood. Here, we use experiments, simulations and theory to demonstrate that fractional skyrmion and bimeron strings can be created in a nematic liquid crystal (LC) through incompatible interfaced topological patterns. Moreover, distinct topological profiles are realized in the same skyrmion string loop. The light-actuated transformations of fractional skyrmion textures in both straight and loop geometry drive colloidal assemblies to exhibit exotic dynamic behaviors. Finally, fractional skyrmions with arbitrary shapes can be used as templates for a variety of exquisite colloidal assemblies. This work provides opportunities for designing new smart material to control self-assembly and transport of colloids.

Autonomous inverse encoding guides 4D nanoprinting for highly programmable shape morphing

Abstract Highly programmable shape morphing of 4D-printed micro/nanostructures are urgently desired for applications in robotics and intelligent systems. However, due to the lack of autonomous holistic strategies throughout the target shape input, optimal material distribution generation, and fabrication program output, 4D nanoprinting that permits arbitrary shape morphing remains a challenging task for manual design. In this study, we report an autonomous inverse encoding strategy to decipher the genetic code for material property distributions that can guide the encoded modeling toward arbitrarily pre-programmed 4D shape morphing. By tuning the laser power of each voxel at the nanoscale, the genetic code can be spatially programmed and controllable shape morphing can be realized through the inverse encoding process. Using this strategy, the 4D-printed structures can be designed and accurately shift to the target morphing of arbitrarily hand-drawn lines under stimulation. Furthermore, as a proof-of-concept, a flexible fiber micromanipulator that can approach the target region through pre-programmed shape morphing is autonomously inversely encoded according to the localized spatial environment. This strategy may contribute to the modeling and arbitrary shape morphing of micro/nanostructures fabricated via 4D nanoprinting, leading to cutting-edge applications in microfluidics, micro-robotics, minimally invasive robotic surgery, and tissue engineering.

A Liquid Crystal Polymer With Thermally‐Induced Deformation and Reversible Fluorescence Switching

AbstractStimuli‐responsive liquid crystal polymers (LCPs) hold significant promises as materials for designing multifunctional soft actuators. Recently, this group explored a novel strategy to develop a multi‐responsive LCP by combining ring‐opening metathesis polymerization (ROMP) with post‐polymerization modification (PPM). The current study aims to advance the approach to design an LCP capable of thermally‐induced deformation and fluorescence switching. ROMP is first employed to synthesize a reactive linear LCP precursor containing aggregation‐induced emission luminogens (AIEgens) with excellent processability, enabling the preparation of arbitrary shapes through various processing techniques. Subsequently, PPM is responsible for anchoring the mesogen alignment of the as‐prepared film and fiber geometries. The obtained cross‐linked LCP films and fibers undergo contraction, bending, unfolding and rolling with increasing temperature. Furthermore, the disruption of mesogen at high temperature weakens the restriction of AIEgen motions, facilitating the switching of the fluorescence property of LCPs. This material design combines the diverse fabrication opportunities, advanced actuation capabilities, and the tunable emission properties of AIEgens, while also enabling the visualization of the actuator's state.

Fundamental mode excitation via Joule-Thomson light expansion in nonlinear optical lattices.

Under linear conditions, power injected from a single waveguide into a multi-core fiber array results in multimode propagation, progressively diminishing the spatial coherence of light. In this work, we introduce a comprehensive approach to mitigate this coherence loss by means of a nonlinear thermodynamic Joule-Thomson expansion. By leveraging the tools of optical thermodynamics, we demonstrate that as light undergoes a sudden transition from a small to a larger nonlinear optical array, it can abruptly drop its optical temperature to near-zero values. During this cooling process, light irreversibly flows into the system's fundamental mode with very high efficiency, synchronizing all elements of the lattice with the input port. We show that this nonlinear effect is highly predictable even in systems of arbitrary geometry and shape and can be controlled precisely by the initial conditions at the input of the array. In particular, for a single injection point, the reduction in optical temperature can be directly determined by the total power, irrespective of the input location.

Ultralight Carbon Tube Foam-Derived SiC Nanofibrous Aerogels with Arbitrary Shape, Excellent Rigidity, and Resilience for Thermal Insulation.

Ceramic aerogels are promising high-temperature thermal insulation materials due to their outstanding thermal stability and oxidation resistance. However, restricted by nanoparticle-assembled network structures, conventional ceramic aerogels commonly suffer from inherent brittleness, volume shrinkage, and structural collapse at high temperatures. Here, to overcome such obstacles, 3D ultralight and highly porous carbon tube foams (CTFs) were designed and synthesized as the carbonaceous precursors, where melamine foams were used as the sacrificial templates to form the hollow and thin-wall network structures in the CTFs (density: ∼4.8 mg cm-3). Then, the arbitrary-shaped silicon carbide (SiC) nanofibrous aerogels (SNFAs) were obtained through a simple chemical vapor deposition (CVD) process on the CTFs. The resulting SNFAs exhibited excellent comprehensive performances: ultralow density (4.2 mg cm-3) and thermal conductivity (21.3 mW m-1 K-1 at room temperature), excellent rigidity (specific modulus: 13.2 kN·m kg-1), and resilient compressibility. The SNFAs could support over 2100 times their weight without visible deformation. Furthermore, the SNFAs also showed exceptional high-temperature thermal stability, which means that they could withstand 1100 °C in an air atmosphere and 1550 °C in an inert atmosphere. These superior comprehensive performances enable SNFAs to be suitable for thermal insulation in harsh environments.