Phase Distribution Research Articles

RGB Mapping: A Dynamic Approach for Flow Pattern Identification and Classification

Thermal-hydraulic modeling and simulation are heavily dependent on the knowledge of flow regimes, which sort multiphase flow patterns into classifications with static boundaries that display characteristic features of flow patterns and phase distributions. Flow regime maps heretofore have been primarily developed mainly for vertical or horizontal pipe orientations by capturing images of flows at varying conditions and assigning them to different flow regimes based on visualization studies. As such, this method is inherently subjective. Furthermore, classifying two-phase flows into regimes with static boundaries is not physical, as two-phase flows undergo gradual changes as they transition from one regime to another. Therefore, such a static approach is not only unphysical but also inaccurate, resulting in the erroneous analysis of two-phase flows. Additionally, subjective observations at such flow conditions are prone to disagreement and inconsistencies in labeling. These difficulties are exacerbated in inclined two-phase flows. In this study, a novel two-phase flow pattern map employing the dynamic red, green, and blue (RGB) color model is presented. The model contains the embedded information of three normalized time-averaged statistics from signals obtained by a dual-ring impedance meter. A database of impedance meter signals from a 25.4-mm-inner-diameter adiabatic air-water inclinable test facility is used to compute statistics for each experimental flow condition. Multiple statistical measures are evaluated, and a principal component analysis is performed for feature selection. By mapping each parameter to intensities of red, green, and blue, a dynamic RGB flow pattern map can be produced in which groups of similar colors are representative of various flow regimes and the dynamic transition characteristics between the flow regimes are characterized physically. Therefore, this new method makes viable the observation of how flow patterns gradually change with respect to angle, as well as the fuzzification or quantification of the uncertainty surrounding experimental transition boundaries.

Multi-frequency instantaneous wavenumber damage imaging method based on ultrasonic guided waves induced by laser point-by-point excitation

ABSTRACT A multi-frequency instantaneous wavenumber damage imaging method based on ultrasonic guided waves induced by laser point-by-point excitation is proposed in this paper. The experiment involved using the Nd:YAG pulsed laser is used as the excitation source to excite ultrasonic guided waves point-by-point in the detection area, and the piezoelectric ceramic transducer is used to receive ultrasonic guided wavefield at a fixed position. The wavefield information at different frequencies is extracted by a three-dimensional Fourier transform. The spatial phase distribution of the extracted guided wavefield with different frequencies is obtained by the Hilbert transform and phase unwrapping method. Then, the wavenumber of each detection point and the dispersion relations of the test piece with different thicknesses are calculated. Based on the calculated dispersion relation, the mapping relationship between the wavenumber and the thickness of the test piece is obtained. Furthermore, based on the obtained wavenumber information and wavenumber thickness mapping relationship, the thickness reduction depth of the defect can be calculated. Finally, the quantitative detection of defects is achieved through data fusion. The proposed method is verified through quantitative detection of the rectangular groove defects and the flat bottom defects with variable thickness and complex contour in the aluminium plate. At the same time, the detection results of the proposed method are compared with those of the single-frequency instantaneous wavenumber imaging method, single-frequency local wavenumber imaging method, and multi-frequency local wavenumber imaging method. In the detection results, the method proposed in this paper presents a better defect detection effect.

Coherence Programming for Efficient Linearly Polarized Perovskite Light-Emitting Diodes.

Although quasi-two-dimensional (quasi-2D) perovskites are ideal material platforms for highly efficient linearly polarized electroluminescence owing to their anisotropic crystal structures, so far, there has been no practical implementation of these materials for the demonstration of linearly polarized perovskite light-emitting diodes (LP-PeLEDs). This scarcity is due to difficulty in orientation and phase distribution control of the quasi-2D perovskites while minimizing the defects, all of which are required to manifest aligned transition dipole moments (TDMs). To achieve this multifaceted goal, herein, we introduce a synergistic strategy to quasi-2D perovskites by incorporating both a trimethylolpropane triacrylate anchoring layer and 18-Crown-6 molecular passivator into the film fabrication process. It is found that the interfacial anchoring layer guides the oriented growth of perovskites along the (110) plane, whereas the molecular passivator reduces the number of defects and homogenizes the crystal phase. As a result, a quasi-2D perovskite film with macroscopically aligned TDM that renders high radiative recombination and the degree of linear polarization (DoLP) is constructed. This "coherence-programmed emission layer" demonstrates highly efficient LP-PeLEDs, not only achieving a maximum external quantum efficiency of ∼23.7%, a brightness of ∼36,142 cd/m2, and a DoLP of ∼38%, but also significantly improving the signal-to-interference-and-noise ratio in a multi-cell visible light communication system.

Generating sub-diffraction microwave needle beam for nondestructive testing by multifunctional transmissive metasurfaces

Sub-diffraction needle beams with high intensity, sub-diffraction focal size, and long depth of focus (DOF) have attracted many researchers’ attention. However, the traditional methods for needle beam generation typically require many devices, such as phase elements, amplitude filters, and lens, which leads to a complex and bulky system and unfavorable for their integration. To address these challenges, we use a single multifunctional transmissive metasurface to convert a linearly polarized plane wave into a needle beam in the microwave range. The guided wave inspired unit cells of the proposed metasurface is designed to simultaneously and independently modulate the polarization and phase of transmitted waves. By imposing the desired polarization and phase distributions on the metasurface, the proposed multifunctional transmissive metasurface can efficiently generate a needle beam with subdiffraction size and extended DOF at 10 GHz when it is illuminated by an x-polarized wave. The proposed metasurface is fabricated, and a sub-diffraction needle beam with good performance is obtained in our measurements. In addition, a proof-of-concept of a high-resolution nondestructive testing experiment based on our designed metasurface is accomplished. Our work is expected to have potential applications in nondestructive testing of materials and structures.

Microstructural characteristics and mechanical response of transient liquid-phase diffusion bonding AlCoCrFeNi2.1 high entropy alloy utilizing BNi-5 interlayer

This study focuses on the microstructural characteristics and mechanical response of the transient liquid phase (TLP) diffusion-bonded joints of AlCoCrFeNi2.1 high entropy alloy. Bonging parameters were chosen and optimized for the AlCoCrFeNi2.1 alloy and the TLP joining mechanism. The relatively complete isothermal solidification zone (ISZ) ensured a reliable connection of the base metal. As the bonding temperature increased from 1060 °C to 1160 °C, the athermal solidification zone (ASZ) disappeared. The homogenization degree of elements in the ISZ continuously increased, the matrix γ phase became fully ordered, and the B2 phase was precipitated, achieving high entropy state in the ISZ of the joint. Additionally, semi-coherent relationships of [0, 1, 1] L12, [0, 1, 1] B2 and (1, 1̅,1) L12, (2̅, 3, 1̅) B2 were detected between the B2 precipitate phase and the L12 matrix. The phase distribution in the ISZ significantly influenced the mechanical properties of the joint. The complete ordering of the matrix phase at 1160 °C eliminated deformation incoordination between the ISZ and the diffusion-affected zone (DAZ). The B2 phase transitioned from precipitating at the grain boundary at lower temperatures to precipitating uniformly in the ISZ, eliminating the weakening effect of the grain boundary and resulting in tensile strength and elongation comparable to the base material. The fracture morphology indicated a mixed fracture mode.

3D distribution of biomineral and chitin matrix in the stomatopod dactyl club by high energy XRD-CT

Stomatopods are ferocious hunters that use weaponized appendages to strike down their pray. The clubs of species such as Odontodactylus scyllarus undergo tremendous forces, and in consequence they have intricate structures, consisting of hydroxyapatite, chitin, amorphous calcium phosphate and carbonate, and occasionally calcite. These materials are distributed differently across the four major zones of the dactyl club: the impact, periodic lateral and medial, and striated regions. While stomatopod clubs and their structure have been studied for a long time, studies have thus far been constrained to 2D mapping experiments with moderate resolution due to difficulties in preparing whole club thin sections, and absorption tomography that gives information on densities but not molecular length scales. To address this problem, and shed light on the structure of entire clubs, we herein used X-ray powder diffraction computed tomography (XRD-CT) using high energy X-rays at the P07 beamline of PETRA-III to allow penetrating the large samples whilst still obtaining high resolution information. This allowed mapping the 3D distribution of diffraction phases including the biomineral apatite and the semi-crystal chitin matrix. This showed that hydroxyapatite forms an envelope around the club, and that chitin forms 2D sheets in the periodic region of the club.

Assessment of compatibility of dextran/PEMA blends by thermal, topologic and viscoelastic analysis

In this study, the compatibility of polymer blends of dextran (DEX) and poly(ethylene-alt-maleic anhydride) (PEMA) was evaluated with their enhanced thermal and dynamic mechanical properties as well as structural and topological properties. Blends were prepared in various ratios via solution casting method. The effects of composition and dispersion on interactions, thermal, viscoelastic and topological properties of the blends were investigated using thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), atomic force microscopy (AFM) and attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy and X-ray diffraction (XRD) analysis. TGA results indicated that blends exhibited higher thermal stability than the individual polymers, with residue percentages increasing from 13.57 % and 11.43 % for DEX and PEMA, respectively, to 27.42 %–16.86 % for the blends at 605 °C. DMA results showed that all blends remained intact at higher temperatures compared to the polymers, with higher Tg values due to the H-bonding interactions confirmed by ATR-FTIR. AFM phase imaging enabled the visualization of miscibility distinctions, revealing that the 30/70 DEX/PEMA blend had a uniform phase distribution and minimal phase shifts, suggesting improved miscibility. In contrast, other blends exhibited more heterogeneous miscibility. These findings highlight that DEX/PEMA blends, with their enhanced thermal and dynamic mechanical properties, have significant potential for various applications.

Non-uniform phase distribution of a tightly focused elliptically polarized vortex beam

Abstract Tight focusing of elliptically polarized vortex beams has been previously studied for optical manipulation, optical information encoding, and so on. Still, there is a lack of research on the status of the phase distribution on the focal plane. In this study, we found that the phase distribution of a tightly focused elliptically polarized vortex beam is non-uniform, i.e., the phase distribution exhibits flatter and steeper regions due to the elliptical polarization of the input vortex beam. It is mentioned that the phase non-uniformity was related to the ellipticity of the polarization of the incident beam. Furthermore, we analyzed the intensity and phase distribution of a tightly focused elliptically polarized vortex beam. We found that the spin angular momentum was converted to the orbital angular momentum because the topological charge of the output beam was greater than that of the input beam. The non-uniform phase distribution of a tightly focused elliptically polarized vortex beam enables control over light–matter interaction, leading to advancements in optical tweezers, quantum information processing, and super-resolution microscopy.

Phase Distribution Dictates Charge Transfer and Transport Dynamics in Layered Quasi-2D Perovskite.

Strategic manipulation of spatiotemporal evolution of charge carriers is critical for optimizing performance of quasi-two-dimensional (2D) perovskite-based optoelectronic devices. Nonetheless, the inhomogeneous phase distribution and band alignment engender intricate energy landscapes, complicating internal charge and energy funneling processes. Herein, we integrate high spatiotemporal resolution transient absorption microscopy with multiple time-resolved spectroscopy and find that asynchronous electron and hole transfers rather than direct energy transfer govern the funneling mechanisms. Notably, the charge funneling pathways and transport behaviors can be modifiable by phase manipulation. The accumulation of small-n phases suppresses the electron funneling toward large-n phases and doubles the carrier diffusion rate from 0.085 to 0.20 cm2/s, yielding a 1.5-fold enhancement in diffusion length. Phase order engineering is further corroborated for facilitating charge separation. Our investigation underscores the prospects of manipulating the phase distribution to control internal charge funneling and transport, thereby substantiating the theoretical foundations for optimizing optoelectronic devices.

Crystallization‐correlated phase separation of polypropylene random copolymers

AbstractEthylene segments are incorporated into stereoregular propylene‐propylene‐propylene (PPP) homo‐sequences to create locally disordered ethylene‐propylene (EP) segments in polypropylene random copolymer (PPR) through a phase separation process, resulting in large quantities of spherical EP rubbery particles for improving impact toughness. However, the manipulation on size and distribution of these spherical EP rubbery phases remains insufficiently understood. In this study, the phase separation of PPR and the influence of crystallization on phase separation were investigated using rheological measurements and small‐angle x‐ray scattering (SAXS) methods. Combined with the isothermal crystallization method, phase separation was differentiated by the crystallization rate. The molecular chain states corresponding to different crystallization conditions were studied to interpret the varying rubbery particle sizes resulting from phase separation. The results showed that phase separation of EP segments from PPP is highly related to crystallization. Isothermal crystallization at temperatures ranging from 110 to 130°C leads to a high degree of phase separation due to the fast crystallization rate, as evidenced by the presence of small quantities of large pores in microscopic observations. This work provides insights into the phase separation of random copolymers and establishes correlations for manipulating the low‐temperature toughness of PPR.

Toward mechanical proprioception in autonomously reconfigurable kirigami-inspired mechanical systems.

Mechanical metamaterials have recently been exploited as an interesting platform for information storing, retrieval and processing, analogous to electronic devices. In this work, we describe the design and fabrication a two-dimensional (2D) multistable metamaterial consisting of building blocks that can be switched between two distinct stable phases, and which are capable of storing binary information analogous to digital bits. By changing the spatial distribution of the phases, we can achieve a variety of different configurations and tunable mechanical properties (both static and dynamic). Moreover, we demonstrate the ability to determine the phase distribution via simple probing of the dynamic properties, to which we refer as mechanical proprioception. Finally, as a simple demonstration of feasibility, we illustrate a strategy for building autonomous kirigami systems that can receive inputs from their environment. This work could bring new insights for the design of mechanical metamaterials with information processing and computing functionalities. This article is part of the theme issue 'Origami/Kirigami-inspired structures: from fundamentals to applications'.

Microstructure and Wear Resistance of FeCrV15 Coatings by Laser Cladding

Improving the surface performance and service life of 60Si2Mn steel is an important issue in agricultural machinery. A FeCrV15 coating layer may exhibit excellent performance in wear resistance. This research focuses on studying the microstructure and wear resistance of the FeCrV15 coating layer at various scanning speeds through laser cladding. Microstructure, phase distribution, surface hardness, and wear resistance of the coating layers are analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), a microhardness tester, and laser confocal microscopy. The results indicate that the FeCrV15 alloy coating consists of γ-Fe, V8C7, and Cr7C3. The microhardness of the FeCrV15 coatings increases with the increase in the scanning speed. At a scanning speed of 8 mm/s, the highest microhardness reaches 727.5 ± 27 HV, approximately 2.5 times higher than the substrate. The friction and wear test of the coating is conducted using a 4 mm diameter Si3N4 ball grinding pair. The coatings prepared at different scanning speeds exhibit lower average coefficients of friction and wear rates compared to the substrate. Both the average coefficient of friction and wear rate decrease with increasing scanning speed. At a scanning speed of 8 mm/s, the lowest average coefficient of friction and the lowest wear rate were observed. The main wear mechanisms of the coating are oxidative wear and adhesive wear, with a small amount of abrasive wear.

Unveiling the mechanical and microstructural properties of SiC reinforced aluminum wires recycled from scraps by friction stir extrusion

Friction Stir Extrusion (FSE) has been proven as an effective solid-state process to directly recycle metal chips into high-quality wires/rods/tubes. However, the demand for Al-based composite wires with enhanced properties is substantial, and achieving a uniform distribution of the strengthening phase within the composite wire by establishing a robust metal/ceramic interface remains a significant challenge. In this study, AA6082 Aluminum alloy wires reinforced with 12.5 vol% SiC particles, exhibiting homogeneous particle distribution and superior mechanical properties, were successfully produced through the FSE technique. The investigation focused on examining the influence of processing parameters and the addition of SiC reinforcement on the microstructure and mechanical characteristics of the extruded wires. Scanning electron microscopy (SEM), Electron Backscatter Diffraction (EBSD), together with microhardness, bending, and tensile tests, were used to comprehensively analyze the resulting properties. The findings demonstrate a substantial enhancement in the wires' mechanical properties due to the SiC particles. Both tool rotation and tool force were varied during the experimental campaign. Notably, the reduction in porosity and grain refinement resulted in a 12.78 % increase in tensile strength and an 18.6 % improvement in microhardness compared to Al 6082 alloy extruded wires. Grain orientation analysis revealed a fully recrystallized microstructure with a weak texture. Furthermore, the study evaluated power consumption and surface roughness while assessing the feasibility of deposition, thereby highlighting the potential application of this technique in advanced additive manufacturing processes.

Spatially distributed low-cross talk vector beams.

A spatially distributed low-cross talk vector beam refers to a vector beam that exhibits different intensities, phases, and polarization states along the propagation direction. This type of vector beam features low-cross talk between beams on different planes and finds extensive applications in optical communications and related fields. However, current technologies face challenges such as intensity interference at different imaging planes and difficulties in the precise control of phases and polarization states, which affect beam quality. In this study, we investigated the beam propagation process and employed a global optimization strategy to precisely control the intensity and phase distribution of the beam fields. This approach ensures that the beam forms the desired complex amplitude distribution in the target region while effectively suppressing cross talk in non-target regions. We utilized the method to generate two beams with complementary intensities and phases. Subsequently, through an interference optical path, we separated these two beams and converted them into orthogonal polarization states. Finally, by superimposing these two beams, we obtained a spatially varying low-cross talk vector beam. We experimentally validated the beam's different optical characteristics and low-cross talk properties on three planes. Our work opens up new prospects, to the best of our knowledge, for holographic technology with capabilities for ultra-fine depth control and polarization multiplexing.

Triple Jump Performance Parameters and Inter-Limb Asymmetry in the Kinematic Parameters of the Approach Run in International and Paralympic-Level Class T46/T47 Male Athletes

Background/Objectives: The triple jump is included in the Paralympic Athletics competition. The aim of the research was to examine the relationship of the phase ratios and the inter-limb asymmetry in the spatiotemporal parameters of the approach run in Paralympic and international-level Class T46/T47 triple jumpers. Methods: Eleven Class T46/T47 male athletes were recorded during the examined competitions. Step length (SL), frequency (SF), and average velocity (ASV) for the late approach run as well as the length and the percentage distribution of each jumping phase (hop, step, jump) were measured using a panning video analysis method. The inter-limb asymmetry was estimated using the symmetry angle. Results: No significant inter-limb asymmetry was found (p > 0.05). In addition, SL, SF, and ASV were not different (p > 0.05) between the steps initiated from the ipsilateral and the contralateral leg regarding the impaired arm. However, the direction of asymmetry for SF was towards the ipsilateral leg to the impaired arm in the majority of the examined athletes. The maximum speed of the approach was correlated with the triple jump distance and the magnitude of asymmetry for AVS was correlated with the vertical take-off velocity and angle for the step. Conclusions: Since the distance of the triple jump related with the peak approach speed added the negative correlation of peak approach speed with the magnitude of the symmetry angle for SL, it is suggested to minimize the asymmetries in the step characteristics during the approach run to improve triple jump performance in Class T46/T47 jumpers.

Corrosion Susceptibility and Microhardness of Al-Ni Alloys with Different Grain Structures

The development of Al-Ni alloys with a controlled microstructure has had a great impact on the field of study of aluminum-based alloys. In the present research, the influence of thermal parameters on the grain structures resulting from the directional solidification process of Al-Ni alloys with different alloy content has been studied. It has also been evaluated how different structures and the distribution of second phases influence the corrosion behavior and microhardness of alloys. The columnar-to-equiaxed transition (CET) was observed to occur when the temperature gradient in the melt decreased to values between 1.3 and 2.9 °C/cm. In addition, a small increase in the microhardness values was observed as a function of the Ni content. When the Ni content increases, the resistance to polarization decreases for samples with equiaxed grain structure throughout the range of compositions studied. Furthermore, the equiaxed grain structure presents higher resistance to polarization values than the columnar grain zone for alloys with a composition equal to or lower than the eutectic composition.

Solute and phase heterogeneous distribution at different scales and its effect on ageing physical phenomena in a laser powder bed fusion produced maraging steel

The Laser Powder Bed Fusion process involves complex thermodynamic and heat transfer mechanisms which results in a complicated understanding of the material’s microstructure and phase transformation processes. In the case of additive manufacturing maraging steels, these present heterogeneous structures which mainly consist of Body-Centred Tetragonal (BCT) martensite and retained austenite (Face-Centred Cubic (FCC) phase structure), unlike conventionally processed material. Research has already been done on the competitive or collaborative nature of austenite growth/reversion and precipitation in these materials. However, for Laser Powder Bed Fusion maraging steels, studies have focused on either the effect of the heterogeneous structures on austenite reversion kinetics or the formation, evolution and behaviour of precipitation. Still, no comprehensive research exists that covers in detail the relation between solute heterogeneity from the meso- to the nanoscale and its influence on both phase distribution and ageing physical phenomena. To do so, multiscale chemical analyses and microstructural characterisation techniques were used to investigate a maraging steel M300 in different transformed conditions: as-built, aged at 480 and 540 °C. The results showed that competing mechanisms during printing caused segregation at the mesoscale, which remains in aged samples. Vaporisation led to Cr segregation, while melt convections caused Ni and Ti depletion at melt pool boundaries. Retained austenite location was found at melt pool boundaries and away from them on the as-built structure. Its preferential location remains unclear. Dissimilarities from conventional material were identified in nanosized clustering and precipitates on aged samples.

Deep learning for pore-scale two-phase flow: Modelling drainage in realistic porous media

In order to predict phase distributions within complex pore structures during two-phase capillary-dominated drainage, we select subsamples from computerized tomography (CT) images of rocks and simulated porous media, and develop a pore morphology-based simulator (PMS) to create a diverse dataset of phase distributions. With pixel size, interfacial tension, contact angle, and pressure as input parameters, convolutional neural network (CNN), recurrent neural network (RNN) and vision transformer (ViT) are transformed, trained and evaluated to select the optimal model for predicting phase distribution. It is found that commonly used CNN and RNN have deficiencies in capturing phase connectivity. Subsequently, we develop a higher-dimensional vision transformer (HD-ViT) that drains pores solely based on their size, regardless of their spatial location, with phase connectivity enforced as a post-processing step. This approach enables inference for images of varying sizes and resolutions with inlet-outlet setup at any coordinate directions. We demonstrate that HD-ViT maintains its effectiveness, accuracy and speed advantage on larger sandstone and carbonate images, compared with the microfluidic-based displacement experiment. In the end, we train and validate a 3D version of the model.

Far field reconstruction of antennas via single‐surface phaseless spherical near‐field scans: A novel approach based on dipole equivalence

AbstractA novel approach is proposed in this paper to reconstruct the far‐field radiation pattern from the phaseless electric field of an antenna scanned on a single near‐field sphere. It adopts the dipole equivalence approach to project the near‐field electric field into a spherically distributed array of electric dipoles. A term representing the error from the linearly correlated portion in the least‐square problem associated with the dipole equivalence, namely the linear correlation error, is introduced. It is demonstrated that by iterative search to minimize the linear correlation error using the covariance matrix adaptation evolution strategy, near‐field phase distributions can be found efficiently from the magnitude‐only near‐field, and the far‐field radiation pattern can be computed. Two representative case studies are given here to validate the proposed method. Results demonstrate good agreements between computations and simulations.

Microstructure and corrosion behavior of Ti-Mo-Zr alloy fabricated by selective laser melting in simulated oral environment

The microstructure of Ti-Mo-Zr alloy fabricated by selective laser melting (SLM) was studied and its corrosion behavior was investigated by a series of electrochemical methods. The results showed that α+β phases of different proportions were formed after heat treatment, the grain size of the alloy treated at 950℃ slightly increased, because of the existence of the original α grain, the orientation of the α grain was not significantly changed by heat treatment below the β transition temperature. However, heat treatment above β transition temperature significantly changed the orientation of α grains. Electrochemical measurements were conducted in artificial saliva solution and artificial saliva solution containing hydrogen peroxide. The results showed that the corrosion resistance of the original Ti-Mo-Zr alloy was better than that of the Ti-Mo-Zr alloy treated at 950°C and worse than that of the Ti-Mo-Zr alloy treated at 1050°C. The differences in corrosion behavior can be attributed to grain size and orientation and phase distribution.