Array Of Holes Research Articles

Improved suspension quality and liquid level stability in stirred tanks with Rotor-Stator agitator based on CFD simulation

The solid-liquid mixing is an important operation unit in the preparation of composites by stirring casting. High quality composite materials need good homogeneity and stable liquid level. In this work, the performances of the Rotor-Stator agitator for solid suspension in stirred tank were investigated through CFD modeling, including the homogeneity, power consumption and liquid level stability. The Eulerian-Eulerian (E-E) multiphase model and the RNG k-ε turbulence model were adopted for modeling the multiphase flow and the turbulence effects, respectively. The effect of various important parameters such as stirring speed, particle size, solid loading and the use of baffles were examined. Adding a stator structure with array holes outside the rotor can optimize the flow pattern, thereby improving the mixing uniformity and liquid level stability. The homogeneity and liquid level stability attained by the Rotor-Stator agitator were better than those for the A200 (an axial-flow agitator) and the Rushton (a radial-flow agitator).

Tunable circular conversion dichroism of single-layer twisted graphene-patterned metasurface

Two-dimensional (2D) chirality-induced asymmetric transmission/reflection has great potential for polarization applications. Usually, asymmetric effects resulting from circular conversion dichroism (CCD) occur in chiral metasurfaces. Here, we propose a single-layer twisted graphene-patterned (with tilted elliptical hole arrays) metasurface and theoretically reveal its tunable CCD in the terahertz (THz) region. The unit cell of the metasurface is achiral. Merely by altering the in-plane orientation of holes for structural 2D chirality, a tunable CCD can be achieved at normal incidence. Interestingly, the reflection phase can be considered an intuitive method to show this metasurface's anisotropy, which complements the conventional CCD measurement in characterizing chiral materials. Furthermore, we can achieve active CCD based on the tunability of graphene. Due to the Fabry-Pérot resonance, a multiband enhancement of CCD spectrum will happen by changing the dielectric layer thickness. The proposed metasurface provides more flexible opportunities for designing active THz devices for polarization manipulation.

Influence of Structural Form on the Acoustic Black Hole Array Coupled with Damping Layers

Because of the characteristics of manipulating bending wave, acoustic black hole (ABH) structures can efficiently concentrate vibration energy in the center. Other than single ABH structures, the ABH array or damping layers can be used to have a better performance in vibration reduction and noise control, which have great engineering application prospects of plate parts. In order to explore the influences of ABH array on vibration and noise reduction, finite element models of two-dimensional ABH array coupled with damping layers were established in this paper to study the effects of arrangements and number of ABH cells on dynamic characteristics. Firstly, this paper analyses the influences of array embedded with three ABH cells on the modal loss factor and vibration characteristics of the structures as well as the effects of different arrangements. Secondly, the array with different number of ABH cells were established to study the effects of the number of elements on the vibration response of the plate. Finally, the structure-sound coupling models were established to study the acoustic radiation characteristics and explain the noise response of the array plate. This study provides a reference for the design and application of the plates embedded with ABH array.

Directional amplified spontaneous emissions from Ag nanohole array with high diffraction orders.

Surface plasmon excitations in metallic hole arrays have been extensively studied in the context of light-matter interaction, since the generated Bloch surface plasmon polariton (Bloch-SPP) exhibits unique properties of nanoscale light confinement, near-field enhancements, and long-range metal surface propagation. In this work, we experimentally demonstrate a plasmonic device that exhibits highly directional emission in visible light; using Ag film with a thickness of 100 nm deposited on a subwavelength porous alumina array as a plasmonic cavity, four-level rhodamine 6G (R6G) is selected as the gain material. It is suggested that a Bloch-SPP with high diffraction orders on a Ag nanohole array can generate a strong local electric field and a high Purcell factor at a nanohole edge. Moreover, directional five-fold enhanced amplified spontaneous emission (ASE) with polarization dependence is observed under a low threshold of 199.9 W/cm2 in the visible light region, which comes from the optical feedback provided by the 2D periodic nanohole array. This work opens up a wide range of applications for real-time tunable wavelength, controlled multimode laser, fluorescence detection, etc.

Engraving Depth‐Controlled Nanohole Arrays on Fused Silica by Direct Short‐Pulse Laser Ablation

AbstractPeriodic nanohole arrangements constitute an important building block of advanced photonic devices. Aside from standard nanofabrication tools, a direct laser‐based approach is introduced here, that enables single‐step and point‐by‐point machining of arrays of holes with subwavelength diameters and depths reaching several micrometers at the surface of fused silica. The method relies on a simple optical arrangement including an axicon combined with an amplitude mask to shape the laser intensity in appropriately truncated micro‐Bessel beams of adjustable length. The suitability and limitations of the technique are investigated to fabricate arrays of cylindrical nanoholes with tunable depths. In particular, the challenge of avoiding crosstalk effects during the laser‐writing process of high‐density arrays is explored. The achievability of square arrays of nanoholes at the surface of fused silica, with diameters down to 200 nm and variable depths from 3 to 20 µm at a spatial density defined by a pitch of 1.5 µm is demonstrated. The performance level shows the potential of the direct‐laser‐processing method towards the realization of integrated devices, offering a highly flexible and cost‐effective alternative technique to current nanofabrication methods.

Damping evolution mechanism of panel embedded with heterogeneous acoustic black hole array

Damping evolution mechanism of panel embedded with heterogeneous acoustic black hole array

Performance of high-resolution CT for detection and discrimination tasks related to stenotic lesions - A phantom study using model observers.

Accurate detection and grading of atheromatous stenotic lesions within the cardiac, renal, and intracranial vasculature is imperative for early recognition of disease and guiding treatment strategies. In this work, a stenotic lesion phantom was used to compare high resolution and normal resolution modes on the same CT scanner in terms of detection and size discrimination performance. The phantom is comprised of three acrylic cylinders (each 15.0cm in diameter and 1.3cm thick) with a matching array of holes in each module. The outer two modules contain holes that are slightly larger than the corresponding hole in the central module to simulate stenotic narrowing in vasculature. The stack of modules was submerged in an iodine solution simulating contrast-enhanced stenotic lesions with a range of lumen diameters (1.32-10.08mm) and stenosis severity (0%, 50%, 60%, 70%, and 80%). The phantom was imaged on the Canon Aquilion Precision high-resolution CT scanner in high-resolution (HR) mode (0.25mm × 0.50mm detector element size) and normal-resolution (NR) mode (0.50mm × 0.50mm) using 120 kV and two dose levels (14 and 21mGy SSDE) with 30 repeat scans acquired for each combination. Filtered back-projection (FBP) and a hybrid-iterative reconstruction (AIDR) were used with the FC18 kernel, as well as a deep learning algorithm (AiCE) which is only available for HR. A non-prewhitening model observer with an eye filter was implemented to quantify performance for detection and size discrimination tasks in the axial plane. Detection performance improved with increasing diameter, dose, and for AIDR in comparison to FBP for a fixed resolution mode. Performance in the HR mode was generally higher than NR for the smaller lumen diameters (1-5mm) with decreasing differences as the diameter increased. Performance in NR mode surpassed HR mode for lumen diameters greater than ∼4mm and ∼5mm for 14mGy and 21mGy, respectively. AiCE provided consistently higher detection performance compared with AIDR-FC18 (48% higher for a 6mm lumen diameter). Discrimination performance increased with increasing nominal diameter, dose, and for larger differences in stenosis severity. When comparing discrimination performance in HR to NR modes, the largest relative differences occur at the smallest nominal diameters and smallest differences in stenosis severity. The AiCE reconstruction algorithm produced the highest overall discrimination performance values, and these were significantly higher than AIDR-FC18 for nominal diameters of 7.14 and 10.08mm. HR mode outperforms NR for detection up to a specific diameter and the results improve with AiCE and for higher dose levels. For the task of size discrimination, HR mode consistently outperforms NR if AIDR-FC18 is used for dose levels of at least 21mGy, and the results improve with AiCE and for the smallest differences in stenosis severity investigated (50% vs. 60%). High-resolution CT appears to be beneficial for detecting smaller simulated lumen diameters (<5mm) and is generally advantageous for discrimination tasks related to stenotic lesions, which inherently contain information at higher frequencies, given the right reconstruction algorithm and dose level.

Three-dimensional inkjet printing and low temperature sintering of silica-based ceramics

The conventional LTCC fabrication route requires a series of costly molding equipment and a complicated manufacturing process. If it is achievable to fabricate ceramics using three-dimensional inkjet printing (IJP) technology, it is anticipated that LTCC components could be designed as a more efficient and flexible additive manufacturing route using IJP technology to co-print ceramic and conductive layers and co-fire them. This research represents the first attempt to utilize IJP technology in the field of LTCC, where we developed a stable SiO2-H3BO3 nanoceramic ink that can be continuously printed through a piezoelectric nozzle with an array of spray holes. The ink was supplemented with selected photosensitive resins to facilitate the curing of the printed layer under ultraviolet light irradiation. Green bodies are sintered at 950° for two hours to obtain ceramic sheets with good surface flatness and microscopic sintering degrees. The tested samples have an ultra-low dielectric constant (εr) of about 2.485 and a low dielectric loss (tan δ) of about 0.0038 (at 1 MHz), while being stable at high temperatures (< 400°) and high frequencies (< 10 GHz), indicating its ability to match the required dielectric properties required for microwave dielectric substrates.

Plasmonic vortices for tunable manipulation of target particles, using arrays of elliptical holes in a gold layer

Here, we numerically prove that light with linear polarization can be coupled to surface plasmon polaritons at an elliptical hole perforated in a gold layer to generate plasmonic vortex (PV). Benefiting from the smooth variation of the minor to major ellipse axes, a gradual variation in the phase profile of the generated PV is achieved. Regarding this, three types of independent arrays of elliptical holes are presented, which can produce uniform and high quality PVs with different topological charges at the center of the arrays. The first array can produce PV with topological charges of + 1 and − 1, depending on the polarization orientation of the incident light. In the second one, the topological charge of the PV can be switched between 0 and + 2, by switching the polarization direction of the incident light. In the third array, a robust PV with topological charge of + 1 is generated independent of possible tolerances in the polarization orientation. In order to use the generated PVs for plasmonic tweezing application, there are side fringes around the central vortex of the arrays that should be eliminated. To produce a single vortex, we propose metal-insulator-metal (MIM) structures, screening excessive fringes and allowing the central PVs to leak out. It is also demonstrated by simulation that target particles, such as gold and polystyrene spheres of subwavelength dimensions, can be efficiently manipulated by our MIM designs, suitable for different applications including local mixing, and applying switchable torque or force to target particles to explore their complete elastic characteristics.

ТЕХНОЛОГІЧНІ ОСОБЛИВОСТІ ВИКОНАННЯ ОПЕРАЦІЙ ПЛУНЖЕРНОГО ФРЕЗЕРУВАННЯ

Milling technological operations are one of the most productive and widespread methods of metalworking. From the point of view of providing the blank with the desired configuration, thesetechnological operations represent the most universal method of processing. Technological operations of plunger milling are now becoming more and more widespread. Plunger milling is used precisely when the use of traditional methods is impossible due to excessive vibrations. Performing technological operations of plunger milling is fundamentally different from performing technological operations of traditional milling. The article contains recommendations that must be followed when performing technologicaloperations of plunger milling. The purpose of the article is to determine the possibility of using any CAM-system to ensure high-quality execution of technological operations of plunger milling. To do this, it is proposed to check whether the CAM-system supports two requirements. The article provides a list of the most common CAM-systems, indicating whether a given software module supports plunger milling. The article proposes a scheme for the implementation of the trajectory of the plunger cutter for the use of any CAM-system in order to ensure the high-quality execution of technological operations of plunger milling. This proposed scheme consists of four main stages. The first stage of the proposed scheme consists of the formation of an array ofholes within the contour of the cavity or other surface being processed. The essence of the second stage of the proposed scheme is to determine the value of the allowance for finishing (depending on the complexity of placing the holes in the contour of the cavity, it is possible to increase the allowance for processing). The third stage of the proposed scheme consists in developing, based on the array of holes that was formed in the first stage, the software code for inserting a cutter into each of the holes in accordance with the coordinates that are specified (by analogy with the development of drilling cycles). The essence of the fourth stage of the proposed scheme is to manually program the removal of the plunger cutter from the walls of the cavity or other surface being processed

Second harmonic generation from aluminum plasmonic nanocavities: from scanning to imaging.

Metamaterials and plasmonic structures made from aluminum (Al) have attracted significant interest due to their low cost, long-term stability, and the relative abundance of aluminum compared to the rare metals. Also, aluminum displays distinct dielectric properties allowing for the excitation of surface plasmons in the ultraviolet region with minimal non-radiative losses. Despite these clear advantages, most of the research has been focused on either gold or silver, probably due to difficulties in forming smooth thin films of aluminum. In the present work, we detect and characterize second harmonic generation (SHG) in the optical regime, emanating from triangular hole arrays milled into thin aluminum films in reflection mode, at normal incidence. We report intense nonlinear responses, year-long stability, and overall superior performances with respect to gold. The robustness of the Al structures and high reproducibility of the measured SHG responses allowed us to investigate changes in the directional emission upon tiny modifications in the structure's symmetry. We also demonstrate large-field instantaneous SHG imaging over areas containing several hole arrays using a recent, non-linear single-spinning disk microscope. Such high spatio-temporal resolution imaging has important applications, e.g., when studying chemical transformations occurring at electrode surfaces during charging and discharging cycles, as well as ageing.

Femtosecond-laser-assisted high-aspect-ratio nanolithography in lithium niobate.

We report the successful fabrication of high-aspect-ratio lithium niobate (LN) nanostructures by using femtosecond-laser-assisted chemical etching. In this technique, a 1 kHz femtosecond laser is first used to induce local modifications inside the LN crystal. Then, selective chemical wet etching is conducted using a buffered oxide etch (BOE) solution. The etching rate in the laser-modified area reaches 2 μm h-1, which is enhanced by a factor of ∼660 in comparison to previous reports without laser irradiation. Such high selectivity in chemical etching helps realize high-performance maskless nanolithography in lithium niobate. In the experiment, we have fabricated high-quality LN nanohole arrays. The nanohole size reaches ∼100 nm and its aspect ratio is above 40 : 1. The minimal period of the LN hole array is 300 nm. Our work paves a way to fabricate LN nano-integrated devices for advanced optic and electronic applications.

Study on influence of ring hole array metamaterial on performance of pyroelectric terahertz detectors

In order to improve the detection performance of 0.1–1THz terahertz wave, a new lithium tantalate pyroelectric terahertz detector based on ring hole array metamaterial is proposed. The quantitative influences of the characteristic parameters such as inner diameter, outer diameter, period and thickness on the transmission bandwidth and transmittance of ring hole array metamaterials are analyzed by simulation. The mechanisms of the influences of different combinations of ring hole array metamaterials and pyroelectric detectors on the detection bandwidth and detection rate of terahertz waves are clarified. The lithium tantalate pyroelectric terahertz detectors of the ring hole array metamaterial ware are fabricated by the MEMS technology. The transmission of the ring hole array metamaterial and the noise equivalent power of the metamaterial detector at different frequencies are tested. The results show that the transmittance of the fabricated ring hole array metamaterial is greater than 40% at 0.25–0.65 THz, and bandpass filtering is realized. When the ring hole array metamaterial and the pyroelectric detector maintain a sufficient distance, the noise equivalent power of the detector at 0.315 THz is 11.29 μW/Hz&lt;sup&gt;0.5&lt;/sup&gt;, which is 6.3% of the 0.1 THz noise equivalent power (outside the bandpass band), so the bandpass detection is achieved. When the ring hole array metamaterial is attached to the detector, the noise equivalent power of the metamaterial detector at 0.315 THz is 4.64 μW/Hz&lt;sup&gt;0.5&lt;/sup&gt;, which is 29.4% that of the detector without the ring hole array metamaterial, so the narrowband detection is achieved. The above conclusions show that the pyroelectric terahertz detector based on the ring hole array metamaterial can realize the bandpass and narrowband detection of specific frequency band in applications such as biological imaging and macromolecular detection.

Process Optimization and Performance Evaluation of TSV Arrays for High Voltage Application.

In order to obtain high-quality through-silicon via (TSV) arrays for high voltage applications, we optimized the fabrication processes of the Si holes, evaluated the dielectric layers, carried out hole filling by Cu plating, and detected the final structure and electric properties of the TSVs. The Si through-hole array was fabricated in an 8-inch Si substrate as follows: First, a blind Si hole array was formed by the Si deep reactive etching (DRIE) technique using the Bosch process, but with the largest width of the top scallops reduced to 540 nm and the largest notch elimidiameternated by backside grinding, which also opens the bottom ends of the Si blind holes and forms 500-μm-deep Si through holes. Then, the sidewalls of the Si holes were further smoothed by a combination of thermal oxidation and wet etching of the thermal oxide. The insulating capability of the dielectric layers was evaluated prior to metal filling by using a test kit. The metal filling of the through holes was carried out by bottom-up Cu electroplating and followed by annealing at 300 °C for 1 h to release the electroplating stress and to prevent possible large metal thermal expansion in subsequent high-temperature processes. The TSV arrays with different hole diameters and spacing were detected: no visible defects or structure peeling was found by scanning electron microscopy (SEM) observations, and no detectable interdiffusion between Cu and the dielectric layers was detected by energy dispersive X-ray (EDX) analyses. Electric tests indicated that the leakage currents between two adjacent TSVs were as low as 6.80 × 10-10 A when a DC voltage was ramped up from 0 to 350 V, and 2.86 × 10-9 A after a DC voltage was kept at 100 V for 200 s.

Selective Area Growth of Cubic Gallium Nitride in Nanoscopic Silicon Dioxide Masks

Herein, the possibilities of nanoselective area growth (NSAG) of cubic gallium nitride on 3C‐SiC/Si (001) pseudo substrates are studied. Growth is masked by SiO2 patterned with hole arrays and groove structures. Nanosphere lithography and block‐copolymer lithography are employed to pattern holes with diameters of 130 and 17 nm, respectively. Electron beam lithography is used to pattern grooves. Patterns are transferred into SiO2 and 3C‐SiC by reactive ion etching with CHF3/Ar and SF6 chemistry, correspondingly. It is possible to demonstrate phase pure nanoselective nucleation of c‐GaN on &lt;001&gt; and &lt;111&gt; facets of 3C‐SiC. Phase pure nucleation of cubic gallium nitride is confirmed by transmission electron microscopy measurements on the nanoscopic scale. A hexagonal fraction of 17.6% is achieved on the macroscopic scale measured by high‐resolution X‐ray diffraction (HRXRD), employing V‐shaped grooves on 4° miscut substrates. Furthermore, the possibility of coalescence after NSAG is demonstrated with the dominant cubic phase.

Performance optimizing and entropy generation analysis of a platinum–stainless-steel segmented microreactor

In this study, stainless-steel-platinum segmented microreactors were designed, their combustion performance was evaluated, and optimized designs were produced. Flames have been stabilized in such microreactors by including holes that provide a low-velocity zone that facilitates flow mixing between the inner and outer tubes of the reactors. However, the optimal number and size of these hole arrays had not been thoroughly explored. Three combustor designs with four or six pores of various sizes and a fixed platinum catalyst area were thus investigated. The combustion performance for various methane-air mixture and hydrogen-air mixture inlet velocities and equivalence ratios was evaluated through experiment and simulation in terms of both the second-law irreversibilities of the reaction and the unburned fuel content in the exhaust gases. The reactor designs were optimized using a Kriging model to reduce the cost of experimentation, and a sensitivity analysis was performed. The hydrogen–air equivalence ratio dominated the combustion efficiency. The six-hole design had the best performance and achieved complete combustion.

Simple analytical model to use in CAD tools for designing FSS devices: plasmonic transmission through hole arrays in thin films

Modeling of nano-structured plasmonic surfaces in optical range has attracted great attention in recent research for its various optical properties such as filtering and enhanced transmission of light. In this paper, we present a simple nanocircuit model that can be integrated in CAD tools to design filters and perfect absorbers FSS devices that are based on plasmonic transmission through thin films structured by hole arrays. To illustrate the model potential, we applied it for both circular and square hole arrays on a silver thin film. The model is demonstrated for different structure parameters (hole size and film thickness) in optical frequencies. We show that the model results compare to the numerical calculations obtained from COMSOL Multiphysics software with acceptable deviation and that the model achieves good matching with previously reported experimental measurements.

Large scanning field laser concurrent drilling system with a five-axis independent control for special-shaped holes.

Five-axis laser scanning technology is an effective drilling method for special-shaped holes. Due to a gap in laser angle-of-incidence (AOI) control within a large scanning field, current technologies are challenging for fabricating large-size holes or special-shaped hole arrays. In this paper, a large scanning field five-axis laser concurrent drilling system was proposed. The laser AOI was independently controlled using two pairs of synchronous deflection mirrors. The laser control deviations under a large scanning field were investigated systematically by simulation and experiment. By establishing a complete correction method, the laser AOI control within a scanning field diameter of up to 35 mm was achieved. A series of special-shaped holes were fabricated concurrently on a 3.6 mm thick glass fiber reinforced plastic (GFRP), verifying that the AOI can be controlled by the five-axis laser scanning system. Our work provides a novel method to increase the scanning field of the five-axis laser scanning technology, expanding the application scope of the five-axis laser processing.

New Horizons for Estimating the Time Since Deposition of Fingermarks: Combining Label-Free Physical Visualization and Electrochemical Characterization.

The time since deposition (TSD) of latent fingermarks (LFMs) serves as "witnesses" for crime scene reconstructions. Nevertheless, existing TSD prediction approaches focused on either physical or chemical aging parameters leading to inaccurate estimation. A novel label-free protocol has been developed, where both physical ridge patterns and lipid oxide (LipOx) degradation kinetics are realized using optical microscopy and scanning electrochemical microscopy (SECM) and combined for TSD prediction. Specifically, the surface interrogation (SI)-SECM titration was utilized to monitor the LipOx degradation in LFM arrays aligned by hole array masks, through which we derived the LipOx degradation function. After establishing the relationship between several titration parameters and titrated area by experimental and numerical simulation methods, the titrated area could be reasonably estimated and subsequently used to calculate the surface coverage of LipOx. Results demonstrated that the tip transient revealed the LipOx coverage of deposited LFMs. Notably, LipOx coverage was found to increase during the first day and then decrease over time, whose degradation rate was susceptible to light. Thus, TSD candidates of an LFM could be limited to two values through the established function. Due to the nonmonotonic trend of LipOx aging, a physical parameter "the gray value ratio (GVR) of furrows to ridges" was proposed to exclude irrelevant TSD through support vector machine (SVM) classification. Ultimately, we predicted TSDs of seven LFMs with estimation errors of 2.2-26.8%. Overall, our strategy, with the outperformed capability of gleaning physical and electrochemical information on LFMs, can provide a truly label-free way of studying LFMs and hold great promise for multidimensional fingerprint information analysis.

Broadband optical transmission through two-dimensional hole arrays

We suggest that a metal film perforated with two-dimensional (2D) hole arrays can support broadband optical transmission. This phenomenon is based on the impedance matching between the perforated metal film and incoming light waves at oblique incidence. Theoretical formulas for the effective impedance of the hole arrays and Brewster angle of broadband transmission have been derived in the infrared regime, taking account of the field penetration effect on the hole walls. With the numerical simulations, the predicted optical effect has also been demonstrated. Compared with the narrow transmission band due to surface-plasmon polariton resonance, our results present a non-resonant, broadband, and robust transmission channel for the 2D hole arrays.