Elliptical Rods Research Articles

Effect of Temperature and Stress on Creep Behavior of (TiB + TiC + Y2O3)/α-Ti Composite

In this study, a (TiB + TiC + Y2O3)/α-Ti composite was prepared by induction skull melting to investigate its creep behavior and microstructure evolution under different temperatures and stresses. The results show that the microstructure of the composite in the as-cast state is a basket-weave structure, and the main phase composition is α lamella, containing a small amount of β phase and equiaxed α phase. The creep life of the composite decreases significantly when the temperature is increased from 650 °C to 700 °C, and the steady-state creep rate is increased by 1 to 2 orders of magnitude. The creep stress exponent at 650 °C and 700 °C is 2.92 and 2.96, respectively, and the creep mechanism of the titanium matrix composite is dominated by dislocation movement. TiB and TiC exhibit synergistic strengthening effects, and Y2O3 remains stable during creep. The reinforcements strengthen the composite by impeding the dislocation movement. The accelerated dissolution of β phase is one of the major reasons for the decrease of creep properties of composite with increasing temperature and stress. Silicide precipitation was observed near the reinforcements and dissolved β-Ti, mainly in elliptical or short rod shapes, which pins dislocations and improves the creep performance of the composite. The results of this study can provide theoretical guidance and practical reference for the subsequent development and application of hybrid reinforced titanium matrix composites.

Focused shear wave beam propagation through a 3D printed human rib cage

Transient elastography (TE) is used in clinical screenings for liver fibrosis. TE generates shear wave motion in the liver by vibration of a piston at the skin. The small, flat piston in current devices radiates shear waves that diverge from the liver, resulting in low SNR and high failure rates, especially in obese patients. Our group recently introduced focused shear wave beams for TE [Cormack et al., IEEE TBME (2024)], in which vibration of a concave piston generates shear waves that converge towards the focal region, thereby increasing SNR for liver stiffness estimation. However, because piston sizes needed for efficient shear wave focusing are larger than the typical intercostal space, the rib cage that lies between the skin and the liver may cause shear wave aberration and influence stiffness measurement. Here, we present measurements of broadband focused shear wave propagation in tissue-mimicking gel in which are embedded 3D printed human ribs. Both straight elliptical rods and anatomically realistic 3D printed ribs are used as aberrators. Measurements are compared to 3D simulations of shear wave beam propagation [Archer et al., JASA (2023)]. Effects of shear wave aberration by the rib cage depend on shear wavelength, piston-to-rib distance, and piston radius and curvature.

Research on the directional characteristics of wind noise emitted by bionic rods

In this paper, the directional characteristics of wind noise emitted by different bionic rods were studied based on a hybrid computational aeroacoustics method. The noise reduction mechanism of surface grooves, pits, and bumps was analyzed, respectively. The basic principle of noise reduction is to reduce the influence of the vortex shedding on the rod by changing the shape of the rod or passive control technology to reduce the dipole sound source. The unsmooth transverse surface will increase the loss of flow on the leading edge of the rod and reduce the vertical effect of vortex shedding on the rod. The convex leading edge of the rod can help to transfer the vertical noise from low frequency to high frequency and reduce the vertical effect of wake vortex shedding to reduce the peak sound pressure level. The cost of those was the increase in the aerodynamic drag and the increase in noise in the flow direction (the increase in the amplitude of drag fluctuation). In particular, the longitudinal v-groove structure on the surface of the elliptical rod can reduce the circumferential aerodynamic noise while keeping the aerodynamic drag coefficient unchanged.

Experimental characterisations of deformation mechanisms in 2D dense assemblies subjected to shearing

This study explored the deformation mechanisms and, in particular, the features of particle pair motions in response to shearing. A specially designed biaxial testing system with a flexible boundary equipped with an image system was set up for experimental tests. The whole testing system was modified from a CKC triaxial testing system. The particle image velocimetry (PIV) technique and close-range photogrammetry were used together to help with the investigation. The test samples TA and TB were made of randomly packed 3 D printed elliptical rods with different particle eccentricities e = 0.1, 0.2, respectively. In the examinations, the motion of a particle pair was divided into three modes, i.e. the contact deformation, the Type 4 rolling and the rigid body motion. It is found that each mode of the motion has different contributions to the sample deformation at different strain levels. The normal component of contact deformation dominates volumetric contraction at small strains and dilation at larger strains. The rigid body rotation only induces a slight dilation in sample TA and even leads to contraction in sample TB as the particles used in TB assembly become more elongated. For the sample distortion, it is mainly due to the rigid body rotation while the normal component of contact deformation makes a second contribution. The tangential component of contact deformation and the Type 4 rolling have relatively small contributions to both volumetric strain and sample distortion. The local volumetric strains arising from the contact deformation (including normal and tangential components) and Type 4 rolling mainly take place at the interfaces between moving particle clusters and vortices, also at the boundaries of micro bands or shear bands. The associated local volumetric strain due to the rigid body rotation mainly occurs inside the shear band.

Rod–Airfoil Interaction Noise at Different Rod Cross Sections and Airfoil Angles

Vortex–body interaction noise from a rod–airfoil model has been investigated experimentally in an aeroacoustic wind tunnel. The model configuration varies by changing either the rod cross section (circular, square, rhombic, and elliptical) or the install angle of the airfoil at three directions (attack angle , sweep angle , and lean angle ) independently. This paper aims to assess the effects of these parameters on the characteristics of vortex–body interaction noise. A near-field microphone array was applied to locate the noise sources on the rod–airfoil model, and a far-field microphone array determined the noise level and radiation directivity. The results suggest that, in the test range, both the elliptical rod cross section and the change of the airfoil install angles can visibly reduce vortex–body interaction noise compared to the baseline rod–airfoil containing the circular rod and the airfoil at zero angles. The interaction noise level decreases with the increase of the eccentricity of the elliptical rod. Of the angles, the most effective way is the change of the sweep angle , which can achieve a noise reduction of 8 dB when reaches 20 deg, but the attack angle has more influence in reducing the vortex shedding frequency. In addition, the noise source distribution of different frequencies also changes with the variation of rod–airfoil configurations. Flow visualization using particle image velocimetry was conducted to analyze the noise change mechanism. The findings from this study are beneficial for engineers in designing low-noise components in several aeronautical and industrial applications.

AE Detection of Crack Extension of Ceramics under Thermal Shock and Characterization of Fracture Mechanics

The mixed mode crack extension behavior of ceramics under thermal shock was dynamically evaluated by a disc-on-rod test and AE measurement. In this test, the transient temperature distribution was measured by an infrared(IR) camera. The microfracture process was dynamically characterized by acoustic emission (AE) measurement, and the crack extension path were observed by a video camera. Using elliptical specimens and elliptical rods, mixed-mode crack extension behavior was characterized. Intermittent crack extension was observed as the temperature distribution changed, and AE signals were detected at the same time. The fracture mechanical parameter of the mixed mode crack extension behavior of ceramics under thermal shock were calculated by the finite element method using the temperature distribution measured by an IR camera. It was confirmed the R-curve behavior in which crack extension resistance increases with crack extension. Consequently, the fundamental insight for the integrity assessment of ceramic structures under thermal shock was obtained.

A generalized model for the prediction of the permeability of mixed-matrix membranes using impermeable fillers of diverse geometry

In this paper, we propose a model to predict the relative permeability of ideal MMMs, which requires the specification of only two geometrical parameters: the relative projected area available for permeation and the relative thickness of the nanofiller. The model, which was initially developed for MMMs with impermeable nano cuboids, provides excellent predictions for nanofillers with a constant relative thickness (i.e., vertical cylindrical and elliptical rods and vertical tubes) with the average prediction error not exceeding 2.1%. For nanofillers with a variable relative thickness (i.e., spheres, horizontal cylindrical and elliptical rods, horizontal tubes), the model is still excellent using the average relative thickness, which is the ratio of the volume fraction and the projected area of the nanofiller. The corresponding average prediction error does not exceed 8%. Except for spherical nanofillers, the model is superior to seven theoretical models commonly used in the literature. After introducing a simple correction factor, the prediction error decreases to 2.3% or less for spheres and horizontal cylindrical and elliptical rods.

Manipulation of topological beam splitter based on honeycomb photonic crystals

The intriguing discoveries of quantum spin Hall effect of electrons and its analogy in photon systems have renovated several concepts in condensed matter physics. Here we emulate topological edge states at microwave frequencies utilizing honeycomb photonic crystals with elliptical rods made of silicon material, and a novel topological beam splitter is implemented and analyzed. Robustness against perturbations provides the beam splitter with extremely strong transmission stability. Noticeably, suppressing the backward transmission of electromagnetic wave mitigates undesirable reflection interference. The numerical analysis results reveal that the splitting ratio obtained is in the range of 0.5–1.5 and the maximum transmittance value can reach up to 97% in this system. Besides, by appropriately adjusting the configuration parameters of photonic crystals, the location of operating frequency can be tuned to match different cases. The proposed structure has tremendous potential applications in the field of all-optical integrated circuits and will promote the practicability of photonic topological insulators in the communication domain

Investigation of anti-corrosive potentials of Cu(II)–Schiff base complex assembled on magnetic Fe3O4, Fe3O4/TiO2 and Fe3O4/SiO2 nanocubes on carbon steel pipelines in 3.0 N HCl

Non-precious Cu(II)-Schiff base complex (CuSB) immobilized on magnetic Fe3O4, Fe3O4/TiO2 and Fe3O4/SiO2 nanocubes were fabricated by a simple and cost-effective route. The as-synthesized materials were categorized using FTIR, XRD, FE-SEM, EDX, TEM, and magnetism (VSM) methods in addition to Monte Carlo (MC) simulations. The FTIR analysis established the efficacious formation of the Schiff base complex@magnetic nanocomposites. The characteristic peak of magnetite Fe3O4 appears at a lower intensity due to the successful CuSB complex immobilization on Fe3O4, Fe3O4/SiO2, and Fe3O4/TiO2. TEM and FE-SEM investigations confirmed that, with CuSB loading on Fe3O4 and it’s coated with SiO2 and TiO2 gradually change its crystallite sizes and the appearance of translucent elliptical rods which is specific for CuSB complex. The corrosion protective potentials of as-produced CuSB@Fe3O4, CuSB@Fe3O4/TiO2 and CuSB@Fe3O4/SiO2 nanocomposites were examined for carbon steel pipelines in 3.0 N HCl solution using potentiodynamic polarization (PDP), linear polarization resistance (LPR) corrosion rate, and electrochemical impedance spectroscopy (EIS) measurements. The outcomes revealed that all CuSB@magnetic nanocomposites impede steel corrosion in 3.0 N HCl more than the corresponding CuSB alone. The value of the protection capacity of the CuSB complex is 81.4%, while for CuSB@Fe3O4, CuSB@Fe3O4/TiO2 and CuSB@Fe3O4/SiO2 nanocomposites are 90.9, 93.4 and 98.1%, respectively. These materials, based on PDP tests, worked as mixed-type additives, and the adsorption route follows the model of Langmuir isotherm. Furthermore, the achieved findings were reinforced by surface inspections of steel specimens using FE-SEM/EDX and FTIR studies.

Experimental characterizations of fabric correlation in 2D rod assemblies subjected to biaxial shearing

This study provides experimental evidence of the correlation between different fabric tensors in 2D granular assemblies subjected to shearing. Two testing assemblies with different elliptical rods were used and the shearing tests were conducted in a tailor-made biaxial cell. Both the rods and cell were produced using the 3D printing technique. Throughout the shearing, three fabric tensors, i.e., the particle orientation-based, the contact normal-based and the void-based fabric tensors, were studied. In particular, to obtain the void-based fabric tensor, the best-fit ellipse method was used, which can better describe the irregular void geometric information compared with the conventional methods described in the literature. In both samples, a strong linear relationship between the anisotropy intensity factors of the three fabric tensors was found. However, such a correlation was not identified when the void-based fabric tensor was quantified using the conventional methods. The discrepancy demonstrates the importance of properly quantifying the fabric tensor, and by using the best-fit ellipse method, the correlation between the fabric tensors can be better observed, which is crucial to understand the constitutive relationship in granules.

Influence of calcination temperature on phase, powder morphology and photoluminescence characteristics of Eu-doped ZnO nanophosphors prepared using sodium borohydride

The prime focus of this work is to synthesize Eu-doped ZnO using sodium borohydride, and analyse the phase formation, functional groups, morphology, elemental mapping and photoluminescence characteristics including emission intensity, R/O ratio, luminescence lifetime, CIE, CCT and colour purity of Eu-doped ZnO phosphors, calcined in a wide range of temperature. XRD analysis confirmed the presence of only ZnO up to 800 °C. Minor phases such as EuBO3 and Eu(BO2)3 were also observed along with the major phase of ZnO at and above 1000 °C. FTIR results suggested that the presence of metal-oxygen, borate (BO3 and BO4) and hydroxyl (O–H/B–OH) groups in the as-synthesized sample may help to form EuBO3 and Eu(BO2)3 phases along with ZnO at higher temperature. Particles were found to be elliptical or elongated rod and polyhedral shape up to 800 °C, and it became nearly spherical and dumb-bell shape at 1000 °C. At high temperature of 1200 °C, the particles were consolidated in nature. Non-homogeneous distribution of Eu3+ ions were observed up to moderate temperature, and it became segregated/clustered in the ZnO matrix at 1200 °C, as seen from EDX mapping. The photoluminescence characteristics revealed an intense broad transition of 5D0 → 7F2 at 613 nm for samples calcined up to 800 °C. However, a splitting nature in 5D0 → 7F2 transition was observed for 1000 °C and 1200 °C samples, due to the non-homogenous distribution of Eu3+-ions along with induced secondary phases. The luminescence decay was analysed with the help of double exponential function, and the average lifetime of the calcined (400 °C) sample was found to be ∼1.43 ns. It was observed that the presence of secondary phases in the calcined (1000 °C and 1200 °C) samples do not hamper, rather moderately improve the photoluminescence behaviour of Eu-doped ZnO. Based on photoluminescence characteristics results, it may be suggested that the prepared samples might be a feasible material for use as a yellowish-orange, red or deep red-emitting phosphors.

Deformations in trapdoor tests and piled embankments

Fill deformation and surface settlement can be induced by differential settlement at the bottom of the fill in piled embankments. The deformation patterns and the relationship between the surface settlement and the differential settlement at the bottom of the fill have not been well investigated. Two-dimensional single-trapdoor, twin-trapdoor, and multi-trapdoor tests, including four tests with geosynthetic reinforcement, were conducted using elliptical steel rods as an analog to soil. The deformation pattern and influence regions in the single-trapdoor tests were evaluated using the measured deformations. The fill deformations in the trapdoor tests followed the Gaussian distribution. The superposition results of these Gaussian distribution curves of the single-trapdoor tests were compared with the measured deformations in the twin-trapdoor and multi-trapdoor tests. The differences between the measured and calculated results indicate that additional interaction occurred between adjacent trapdoors. The deformation shapes of the fill at the bottom of the geosynthetic-reinforced and unreinforced test sections were different. However, the settlement pattern at the elevation level above 1.5 times the clear spacing of pile caps followed the same Gaussian distribution curve, if the volumetric settlement was the same. A method for predicting the surface settlement of 2D piled embankments is then presented.

Low Dimensional Channel Drop Filter for CWDM Optical Communication Networks

This work presents salient features of an optical wavelength channel drop filter based on two-dimensional photonic crystal technology. The photonic band gap of two-dimensional Photonic Crystal (2-DPC) channel drop filter has been obtained by using plane wave expansion (PWE) method. The parameters of the channel drop filter have been optimized for telecommunication wavelengths 1611 nm and 1631 nm with a refractive index contrast of 3.79 and 3.96 using Gallium Antimonide (GaSb) dielectric material. The number of dielectric rods in X and Z directions were taken as 21, and 20, respectively with a spacing of 540 nm of having elliptical rod radius 0.15µm & 0.1 µm. The proposed design gives around 98% dropping efficiency with a good quality factor about 352. This ultra-compact structure is proposed which can be used for Coarse Wavelength Division Multiplexing (CWDM) applications and photonic integrated circuits.

Engineering fragile topology in photonic crystals: Topological quantum chemistry of light

In recent years, there have been rapid advances in the parallel fields of electronic and photonic topological crystals. Topological photonic crystals in particular show promise for coherent transport of light and quantum information at macroscopic scales. In this work, we apply for the first time the recently developed theory of "Topological quantum chemistry" to the study of band structures in photonic crystals. This method allows us to design and diagnose topological photonic band structures using only group theory and linear algebra. As an example, we focus on a family of crystals formed by elliptical rods in a triangular lattice. We show that the symmetry of Bloch states in the Brillouin zone can determine the position of the localized photonic wave packets describing groups of bands. By modifying the crystal structure and inverting bands, we show how the centers of these wave packets can be moved between different positions in the unit cell. Finally, we show that for shapes of dielectric rods, there exist isolated topological bands which do not admit a well-localized description, representing the first physical instance of "fragile" topology in a truly noninteracting system. Our work demonstrates how photonic crystals are the natural platform for the future experimental investigation of fragile topological bands.

Refractive index sensor based on evanescent field effects in hollow core PCF for detection of analytes over extended E+S+C+L+U communication bands

We present an innovative platform for photonic crystal fiber (PCF) based refractive index (RI) sensor for the detection of analytes. Our PCF operating on the principle of a single mode is spliced with multi-mode fiber on both sides. This PCF contains an empty core, surrounded by elliptical plasma dielectric rods suspended in solid microstructured cladding for different pump signals over the extended range of E + S + C + L + U communication bands. The empty core of this photonic device is injected with analytes leading to generation of an evanescent field. The doping of boron is subjected to significantly diminish the upgraded refractive index of silica which ingresses special capabilities that endow an outstanding potential to PCF for the profoundly intense pulse laser. We present structure with over the extended E-band (1360-1460 nm) ultra-flat anomalous dispersion below −50 ps/nm/km and over the ultra-long U-band (1625–1675 nm) flat near zero anomalous dispersion with high birefringence dedicated to sensing application over the entire communication band. Our designed PCF shows better performance for both high contribution and asymmetric shape of plasma dielectric rods and is strongly sensitive to the refractive index of analytes injected in the core of the PCF.

Local responses in 2D assemblies of elliptical rods when subjected to biaxial shearing

This study explored the characteristics of local responses in 2D assemblies of elliptical particles when subjected to shearing. A biaxial shearing system was designed for this investigation, and two assemblies of elliptical rods with different eccentricities were used. To quantify the local responses, the assemblies were partitioned into individual Set Voronoi cells, and in this partition, the scaling method was proposed to tackle the interparticle overlapping problem. Then, in the Voronoi cells, the local strain was measured, accounting for the effect of interparticle rotation, and the local structures in terms of the local volume and anisotropy were estimated using Minkowski functionals. In the two samples, discontinuity by shearing was observed for these local quantities. Before the peak stress, the local strain developed randomly and the local volume followed a k-gamma distribution. After shearing, shear band and a mixed k-gamma distribution of the local volume emerged. For the local anisotropy, the variation inside shear band was significantly increased by shearing. Finally, the responses inside and outside the shear band were taken out separately for analysis, and the free-volume model was used to explain the differences between these two regions.

Parallel direct writing achromatic talbot lithography: a method for large-area arbitrary sub-micron periodic nano-arrays fabrication

Metasurfaces with complex periodic nanoarrays have attracted a large amount of attention over the past decades due to their pronounced plasmonic and photonic properties. Though various metasurface properties have been theoretically and experimentally investigated, the realization of practical metasurface applications remains a big challenge due to very limited large-area complex nanostructure fabrication. In this paper, we demonstrate a parallel direct writing achromatic Talbot lithography (DW-ATL) technique for large-area arbitrary sub-micron periodic nano-arrays fabrication. By using a laser interferometer, the sparse hole/dot arrays obtained by ATL could be stitched precisely between discrete multiple exposures. Complex sub-micron periodic nanoarrays, such as elliptical discs, rods, L-shaped and Y-shaped periodic nanoarrays, with a sub-hundred nm resolution were fabricated over an area of ∼mm2.

Performance of bi-directional elliptical rolling rods for base isolation of buildings under near-fault earthquakes

Rolling base isolation system provides effective isolation to the structures from seismic base excitations by virtue of its low frictional resistance. Herein, dynamic analysis of flexible-shear type multi-storey building mounted on orthogonally placed elliptical rolling rod base isolation systems subjected to bi-directional components of near-fault earthquake ground motions is presented. The orthogonally placed rods would make it possible to resist the earthquake forces induced in the structure in both the horizontal directions. The curved surface of these elliptical rods has a self-restoring capability due to which the magnitude of peak isolator displacement and residual displacement is reduced. The roughness of the tempered curved surface of the rollers dissipates energy in motion due to frictional damping. The seismic performance of the multi-storey building mounted on the elliptical rolling rod base isolation system is compared with that mounted on the sliding pure-friction and cylindrical rolling rod systems. Parametric studies are conducted to examine the behavior of the building for different superstructure flexibilities, eccentricities of the elliptical rod, and coefficients of friction. It is concluded that the elliptical rolling rod base isolation system is effective in mitigation of damaging effects of the near-fault earthquake ground motions in the multi-storey buildings. Even under the near-fault earthquake ground motions, the base-isolated building mounted on the elliptical rolling rods shows considerable reduction in seismic response. The isolator displacement with the elliptical rolling rod base isolation system is less in comparison to the pure-friction and cylindrical rolling rod systems.

Rigorous Coupled Wave Analysis for Plasmonic Nanoparticles

Electromagnetic simulation packages for nanoparticles have become of interest for science and engineering community because of interesting properties of nanomaterials, such as, plasmonics and localized field enhancement. There are several approaches to calculate electromagnetic wave responses including time domain and frequency domain; each approach does have its own pros and cons. In this paper, we discuss basic principle of Rigorous coupled wave analysis (RCWA) and some key issues of 2D Rigorous Coupled Wave Analysis (RCWA) for nanoparticle simulation, such as, the computing demands (long computation time and memory consumption) and staircase approximation. We also suggest some feasible approaches to get around the issues and speed up the calculation, such as, employing Li Feng Li’s RCWA algorithm for circular and elliptical rods, making use of the symmetry of spherical shape particles to reduce redundancies in computation and building up an Eigenvector/Eigenvalue database of difference radii of disks, so that these disks can be stacked together to form various sizes of nanospheres.

Design of ultra-flattened nearly zero dispersion and ultrahigh non-linear slot microfibres with ultrahigh birefringence

We proposed a new simple design of microfibre employing an elliptical silica rod in the centre of fibre core region as a slot core for the purpose of controlling the chromatic dispersion properties of the microfibre and enhancing the performance of non-linearity and birefringence. The simulation results show that the proposed slot microfibre has ultra-flattened near-zero dispersion of 0.94 ps/(nm km) for quasi-TE mode over a 50-nm wavelength range, ultrahigh birefringence up to the order of 10−1, and ultrahigh non-linear coefficients of 38.35 and 37.92 W−1 m−1 for the fundamental quasi-TE mode and quasi-TM mode at the wavelength of 1.55 μm. The outstanding advantage of this new design is that nearly zero ultraflattened dispersion, ultrahigh modal birefringence and ultrahigh non-linearity can be realized simultaneously simply using a slot fibre core. Benefiting from its excellent performance, the proposed slot microfibre will have great potential for all-optical signal processing applications.