Array Of Rods Research Articles

Audible bandgaps in phononic sonic crystals for educational demonstration

This experiment explored the use of phononic sonic crystals (PSCs) as an educational tool to demonstrate basic principles of wave propagation and phononics. Phononic crystals are periodic structures that attenuate a range of frequencies—called a bandgap—where the periodicity is on the order of the wavelength. Two PSCs were designed, constructed, and tested, to demonstrate the relationship between periodicity and bandgap frequency. The band structure of a 2D array of cylindrical rods was numerically constructed using eigenmode analysis in a finite element simulation. Based on the numerical simulations, two PSC spacings were selected for fabrication with bandgaps in the audible range of human hearing: a 3.5 cm spacing corresponding to a bandgap centered around 3200 Hz and a 6 cm spacing corresponding to a bandgap centered around 5600 Hz. A swept tone was transmitted through both PSCs and the resulting transmission curves were analyzed. The smaller spaced PSC was found to produce a bandgap from 5350z to 6000 Hz, with a 95% transmission drop; and the large PSC was found to produce a bandgap from 2800z to 3750 Hz with an 84% transmission drop. Both crystals were presented at the University of Illinois Urbana-Champaign’s Engineering Open House in April 2024, and their attenuations in the bandgap frequencies were perceived audibly.

Improving the sensitivity of a plasmonic photonic crystal fiber temperature sensor by introducing an array of nanoscale gold rods

Improving the sensitivity of a plasmonic photonic crystal fiber temperature sensor by introducing an array of nanoscale gold rods

Effect of ambient wind on horizontal flame spread over discrete multi-column fuel arrays

The flame spread behaviors of discrete charring fuels are significantly influenced by ambient wind. This paper studied the horizontal flame spread characteristics of discrete birch rod arrays under ambient wind experimentally and theoretically. Here, seven kinds of array spacings (denoted by S, 7–19 mm) and four kinds of wind speeds (denoted by U, 0.5–2.0 m/s) were designed to develop 28 experiments. The experimental results show that the flame inclination angle decreases as wind speed increases. The non-dimensional flame length and the non-dimensional heat release rate are also found to be correlated, and two ignition modes under the action of ambient wind were differentiated. The flame spread rate and wind speed have a linear relationship based on experimental data. The ratio of wind speed to fuel loading is introduced to further examine the variation of flame spread rate. In this article, a heat transfer model is established by simplifying discrete flame spread process and incorporating both radiative and convective heat transfer. A prediction model for flame spread rate is presented, which aligns well with the experimental results. Finally, the mass loss rate under the ambient wind is discussed.

Pressurized water reactor fuel corrosion-related unidentified deposit and its related safety issues – I. Corrosion product deposition and heat transfer

CRUD depositions on fuel cladding are the main cause of power shift and localized corrosion in nuclear power plants. This paper is the first of a three-part study concerning the formation mechanism of CRUD depositions and its related heat transfer issues. In this paper, CRUD depositions are obtained under subcooled boiling conditions in 2 × 2 rod array channels via accelerated deposition method to explore corrosion product deposition and its feedback on heat transfer. Imbalance of deposition and erosion at initial stage causes fouling resistance to increase first and then decrease. CRUD growth is proposed as a relatively pure fouling process combining soluble precipitation and particulate aggregation. Through high-resolution characterizations, boiling chimney diameters span from 3 μm to a dozen microns. Principal components are nickel ferrite and nickel elemental with Fe/Ni ratio of 1.9:1. Static contact angle decreases to less than 30°. Effective CRUD thermal conductivity decreases with the increase of heat flux with 1.3866 W/(m × K) on average. The results of this study provide a precise method for understanding corrosion product deposition and its impact on heat transfer to further establish accurate CRUD-related models and predict CRUD-related safety issues.

Design of photonic topological corner states for electrically pumped terahertz quantum cascade laser

Photonic topological corner states (PTCS) represent discrete zero modes whose frequencies stay in the topological bandgap and wavefunctions exhibit strong spatial localization, which is highly desirable for efficient surface-emitting lasers. While being extensively investigated in optically pumped lasers, the electrically pumped PTCS lasers are merely reported due to the lack of suitable configurations. In this paper, we propose a photonic cavity design based on the PTCSs that can be applied for electrically pumped terahertz quantum cascade lasers (QCLs). The cavity is constructed by following the canonical trivial-nontrivial domain, where the nontrivial domain with expanded and merged four QCL rods is surrounded by the trivial domain with shrunk and merged four QCL rods. Both domains follow the 2D Su–Schrieffer–Heeger (SSH) model. To further construct a fabrication-favorable 3D device, the designed QCL rod array is connected by 2D veins, which functionalize simultaneously as the intermedium for enhanced inter-/intra-cell coupling and the conductive connection to the device. The 3D numerical calculation is finally investigated.

Porous structures impact on particle dynamics of non-Brownian and noncolloidal suspensions

This study aims to provide valuable insights into the impact of porous structures on particle dynamics in non-Brownian, non-colloidal suspension flows at very low Reynolds numbers. Two experimental approaches, Particle Image Velocimetry (PIV) with refractive index matching and Optical Flow Tracking Velocimetry (OFTV) were employed to analyze very dilute suspensions over various porous media models. The study considered three different porous structures with permeabilities ranging from 0.7 to 0.9 and three different thicknesses ranging from 0.2 cm to 0.5 cm, while the suspension bulk volume fraction was maintained at 3 %. In the PIV analysis, we observed that decreasing the porous permeability resulted in the maximum velocity location within the free flow region moving closer towards the interface between the flow and the porous media. We further quantified the effect of the porous structure on the suspension by characterizing interface properties, such as dimensionless slip velocity, shear rate, and slip length. These interface properties were found to be influenced by both the thickness and permeability of the porous media. Next, we analyzed particle migration due to the presence of porous structures using OFTV for very dilute suspensions of 1 %, 2 %, and 3 %, considering a porous medium with known physical properties and thickness. The study revealed two local concentration maxima: one within the free flow region on top of the rod arrays used to create the porous structure and a second along the rods' centerline inside the porous media model.

Terahertz Polarization Isolator Using Two-Dimensional Square Lattice Tellurium Rod Array.

A novel terahertz polarization isolator using a two-dimensional square lattice tellurium rod array is numerically investigated at the interesting band of 0.22 THz in this short paper. The isolator is designed by inserting six hexagonal tellurium rods into a fully polarized photonic crystals waveguide with high efficiency of -0.34 dB. The TE and TM photonic band gaps of the 7 × 16 tellurium photonic crystals are computed based on the plane wave expansion method, which happen to coincide at the normalized frequency domain from 0.3859(a/λ) to 0.4033(a/λ), corresponding to the frequency domain from 0.2152 to 0.2249 THz. The operating bandwidth of the tellurium photonic crystals waveguide covers 0.2146 to 0.2247 THz, calculated by the finite element method. The six hexagonal tellurium rods with smaller circumradii of 0.16a serve to isolate transverse electric waves and turn a blind eye to transverse magnetic waves. The polarization isolation function and external characteristic curves of the envisaged structure are numerically simulated, which achieves the highest isolation of -33.49 dB at the central frequency of 0.2104 THz and the maximum reflection efficiency of 98.95 percent at the frequency of 0.2141 THz. The designed isolator with a unique function and high performance provides a promising approach for implementing fully polarized THz devices for future 6G communication systems.

Highly Efficient Terahertz Waveguide Using Two-Dimensional Tellurium Photonic Crystals with Complete Photonic Bandgaps

A novel, highly efficient terahertz fully polarized transmission line is designed by two-dimensional tellurium photonic crystals consisting of square lattice rod arrays with a complete photonic bandgap. The TE and TM photonic bandgaps of the tellurium photonic crystals, which are computed by plane wave expansion, happen to coincide, and the complete photonic bandgap covers from 2.894 to 3.025 THz. The function of the designed waveguide is simulated by the finite element method, and the transmission characteristics are optimized by accurately adjusting its structural parameters. The transmission efficiency of the waveguide for TE mode achieves a peak value of −0.34 dB at a central frequency of 2.950 THz and keeps above −3 dB from 2.82 THz to 3.02 THz, obtaining a broad relative bandwidth of about 6.84 percent. The operating bandwidth of the tellurium photonic crystals’ waveguide for TM mode is narrower than that of TE mode, whose relative bandwidth is about 4.39 percent or around 2.936 THz above −5 dB. The designed terahertz photonic crystals’ waveguide can transmit both TE and TM waves, and not only can it be used as a high-efficiency transmission line, but it also provides a promising approach for implementing fully polarized THz devices for future 6G communication systems.

A tunable flat terahertz lens using Dirac semimetals: a simulation study

We propose and design a flat and tunable terahertz lens achieved through a two-dimensional photonic crystal composed of an array of rods made of a Dirac semimetal placed in air as the background medium. The structure of interest is a graded index photonic crystal, made possible by the slight variations in the rods’ radii in a direction perpendicular to the direction of the light propagation. Dirac semimetals' ability to respond to variations in their Fermi energy level manifested as a change in the refractive index provides the tunability of our proposed lens. The interaction of electromagnetic waves with the designed structure is investigated for both transverse magnetic and transverse electric polarizations using two-dimensional finite-difference time-domain method.

A novel structure design of barium strontium titanate piezoelectric coating on titanium surface enhanced its response to low-intensity pulsed ultrasound

The piezoelectric effect was an electromechanical conversion effect that can accelerate the bone repair process, relying on mechanical forces for excitation. The design of a piezoelectric coating on titanium alloy surface that can respond to small loads was an urgent problem to be solved for its application in bone repair. In this work, a strontium barium titanate rod array coating was prepared on titanium surface by designing the microstructure and composition. The formation mechanism of barium strontium titanate array structure was analyzed. The barium strontium titanate rod array coating represented excellent piezoelectric properties. The surface potential distribution of barium strontium titanate rod with different conditions was simulated. Interestingly, the surface potential distribution results of the barium strontium titanate rod array showed that the positive and negative potential were distributed simultaneously, which was further confirmed by mineralization results. The strontium barium titanate rod array coating showed no toxicity to osteoblasts. The coating surface was covered by osteoblasts after 5 days of co-culture, which showed good osteoblast proliferation and adhesion. The research results will provide data support and research ideas for the clinical application of biological piezoelectric coatings on titanium and titanium alloys surface.

Oblique illumination-induced transformation between the FP and the Fano resonances through an all-dielectric metasurface.

We demonstrate the angular dispersive transmission properties of electromagnetic fields with both the Fabry-Pérot (FP) resonances and Fano resonances through an all-dielectric metasurface consisting of a silicon bar array over the silicon dioxide slab. More specifically, when the normal incidence is casting over the metasurface, solely FP resonances will be achieved, and the silicon rod array can be equivalent to another dielectric combining with the silicon dioxide substrate. On the other hand, the Fano resonances will become dominant when the metasurface is under the wide-angular oblique illumination, raising the asymmetry in the silicon bar array to function as toroidal dipoles and electric quadrupoles and thus enable the proposed all-dielectric metasurface to achieve different resonances with the variation of different angular illuminations.

Acoustic 4 × 2 encoder based on linear waveguides in two-dimensional solid-solid phononic crystals

The paper proposes a design for an acoustic 4 × 2 encoder that incorporates acoustic waveguides within a two-dimensional square lattice phononic crystal structure. The encoder's structure comprises of a nylon matrix embedded with a 33 × 30 molybdenum rod array, featuring four input ports and two output ports. The simulation results demonstrate that the proposed structure can effectively achieve the acoustic 4 × 2 encoder functionality. To evaluate the performance of the acoustic 4 × 2 encoder, we analyzed the transmission spectrum using the finite element method (FEM).

Experimental investigation on distribution of boric acid in a vertical 1 × 2 rod array channel

During the reactor operation, the mixing mass flow of boron acid caused by diversion cross-flow, turbulent mixing and void drift changes the boron concentration distribution in the coolant and affects the amount of boron in the Chalk River Unidentified Deposit (CRUD). Accumulation of boron within the porous crud layer on the fuel rods in the cores of pressured water reactors (PWR) results in the crud-induced power shift (CIPS), threatening the operation safety of reactors. In order to obtain the mixing mass flow of boric acid between adjacent channels, a vertical test channel containing two subchannels simulating a PWR fuel rod bundle is constructed. Using this channel, flow distributions and mixing mass flow of boric acid are measured for single-phase and two-phase air–water flows. The measurements show that the boric acid distribution is affected by turbulent mixing for single-phase flow and the mixing mass flow of boric acid increases with the Reynolds number. For two-phase flow, the bubble-induced turbulence enhances the turbulence intensity of the liquid flow, the mixing mass flow of boric acid increases with the increase of void drift and reaches the maximum in the slug flow. The experimental data is used to support the development and validation of a new transverse source term model of boron mixing. The comparison result shows the significant improvement of the code prediction.

Experimental investigation of radiative heat propagation in a simplified generic packed bed

A novel test rig for the investigation of radiative heat transfer in packed beds has been developed and is introduced with representative experimental results. The individual components and the calibration are discussed. The generic packed bed is realized in a simplified way by an arrangement of parallel rods, which represent particles in pseudo-2D. In this arrangement, electrically heated rods provide the radiation propagating through the rod array to heat the passive counterparts. A sophisticated temperature-control scheme with a large number of thermocouples and infrared-imaging provides in-depth information about heat transfer in the system. Spectral radiation intensities are determined with a Fourier-transform infrared spectroscopy, which has been modified and validated for this specific application. In order to compare the influence of different surface properties of particles on the heat propagation and surface reflections, rod samples made of stainless steel and magnesium oxide are used. The influence of material properties becomes clearly visible by comparing the high radiation intensities resulting from a stainless steel rod array to the same geometry built from magnesium oxide rods. In addition, the influence of the surface properties is particularly evident in the infrared images since the reflections are significantly higher for the stainless steel samples than for the magnesium oxide samples. The experimental results in the current work demonstrate the ability of the test rig to provide data with a well-defined accuracy as a validation base for numerical radiation simulations in packed beds.

Ultrafast dense DNA functionalization of quantum dots and rods for scalable 2D array fabrication with nanoscale precision.

Scalable fabrication of two-dimensional (2D) arrays of quantum dots (QDs) and quantum rods (QRs) with nanoscale precision is required for numerous device applications. However, self-assembly-based fabrication of such arrays using DNA origami typically suffers from low yield due to inefficient QD and QR DNA functionalization. In addition, it is challenging to organize solution-assembled DNA origami arrays on 2D device substrates while maintaining their structural fidelity. Here, we reduced manufacturing time from a few days to a few minutes by preparing high-density DNA-conjugated QDs/QRs from organic solution using a dehydration and rehydration process. We used a surface-assisted large-scale assembly (SALSA) method to construct 2D origami lattices directly on solid substrates to template QD and QR 2D arrays with orientational control, with overall loading yields exceeding 90%. Our fabrication approach enables the scalable, high fidelity manufacturing of 2D addressable QDs and QRs with nanoscale orientational and spacing control for functional 2D photonic devices.

Performance of a Thermally Regenerative Ammonia-Based Flow Battery with 3D Electrodes Composed of Copper Rod Arrays

Performance of a Thermally Regenerative Ammonia-Based Flow Battery with 3D Electrodes Composed of Copper Rod Arrays

Heterostructured Interface Enables Uniform Zinc Deposition for High-Performance Zinc-Ion Batteries.

Zinc metal has considerable potential as a high-energy anode material for aqueous batteries due to its high theoretical capacity and environmental friendliness. However, dendrite growth and parasitic reactions at the electrode/electrolyte interface remain two serious problems for the Zn metal anode. Here, the heterostructured interface of ZnO rod array and CuZn5 layer is fabricated on the Zn substrate (ZnCu@Zn) to address these two issues. The zincophilic CuZn5 layer with abundant nucleation sites ensures the initial uniform Zn nucleation process during cycling. Meanwhile, the ZnO rod array grown on the surface of the CuZn5 layer can guide the subsequent homogeneous Zn deposition via spatial confinement and electrostatic attraction effects, leading to the dendrite-free Zn electrodeposition process. Consequently, the derived ZnCu@Zn anode exhibits an ultra-long lifespan of up to 2500h with symmetric cells at the current density and capacity of 0.5mAcm-2 /0.5mAhcm-2 . Besides, a remarkable cyclability (75% retention for 2500 cycles at 2Ag-1 ) is achieved in the ZnCu@Zn||MnO2 full cell with a capacity of 139.7mAhg-1 . This heterostructured interface with specific functional layers provides a feasible strategy for the design of high-performance metal anodes.

Efficient 1×2, 1×4, 1×8 and 1×16 photonic crystal filters/power splitters based ring resonators for modern passive optical network PON

In this paper, we propose a new architecture of [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text] optical filter/power splitters operating around 1.55[Formula: see text][Formula: see text]m, based on a CPs 2D photonic crystal ring resonator for Modern Passive Optical Network (PON). This type of functionality, filtering/power splitting is introduced in this work for the first-time according literature. The designed device consists of a square array of GaAs dielectric rods immersed in air. The structure is designed and successfully simulated by the finite element method using the software COMSOL Multiphysics. From the results obtained, we note that the beam is evenly distributed for all output ports with total efficient transmissions of about 99.6%, 98.8%, 97.1% and 96.8% and low insertion losses of about 0.017, 0.052, 0.128, and −0.14[Formula: see text]dB for the [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text] filter power splitter successively.

Effects of orientational and positional randomness of particles on photonic band gap

A recent work [PRL, 126, 208002 (2021)] has explored how thermal noise-induced randomness in a self-assembled photonic crystal affects photonic band gaps (PBGs). For the system of a two-dimensional photonic crystal composed of a self-assembled array of rods with square cross sections, it was found that its PBGs can exist over an extensive range of packing densities. Counterintuitively, at intermediate packing densities, the transverse magnetic (TM) band gap of the self-assembled system can be larger than that of its corresponding perfect system (rods arranged in a perfect square lattice and having identical orientations). Due to shape anisotropicity, the randomness in the self-assembled system contains two kinds of randomness, i.e., positional and orientational randomness of the particles. In this work, we further investigate how PBGs are influenced solely by positional or orientational randomness. We find that compared to the perfect situation, the introduction of only orientational randomness decreases the transverse electric (TE) band gap while having no obvious effects on the transverse magnetic (TM) band gap. In contrast, the introduction of only positional randomness decreases the TE band gap significantly, while it can widen or narrow the TM band gap, depending on the parameter range. We also discuss the thermal (i.e., self-assembled) system where two kinds of randomness are present. Our study contributes to a better understanding of the role orientational randomness and positional randomness play on PBGs, and may benefit the PBG engineering of photonic crystals through self-assembly approaches.

Experimental Study Of Characteristics Of Boundary Layer Flows With Pressure Shielding

Abstract In this study, boundary layer flows over a flat plate with a canopy of an array of rods are experimentally investigated with PIV measurements. The experiments were carried out in a liquid tunnel, where the refractive index of the transparent liquid is matched with that of transparent rods in the array. The statistics of the velocity data at multiple planes show the change of the flow patterns produced by the rod array. The pressure field was calculated from the velocity data through solving the pressure Poisson equation. The power spectral density of the pressure fluctuations, quantifying the sound pressure level, shows that the rod array causes the attenuation of the pressure fluctuations both below and above the rod array. The characteristic flow patterns altered by the rod array were examined by the dynamic mode decomposition. The uncertainty of the measurements was discussed.