Rectangular Holes Research Articles

Study on the hydrogen leakage diffusion behavior by obstacles in confined spaces

In this paper, a combination of experimental and numerical simulation is used to investigate the effects of obstacles and leakage hole shapes on the leakage diffusion pattern and hydrogen concentration. A small-size cubic geometry model of 0.47 m × 0.33 m × 0.20 m is used to calculate the concentration of the leakage model in the confined environment. The results show that the influence of the Q1-Turbulent Flow obstacle model on hydrogen leakage and diffusion is more serious than that of the Q2-Laminar Flow, the gas in the upper part of the model is easier to accumulate, the hydrogen concentration is higher, and it takes longer to finally reach a stable state. Rectangular leakage holes have a larger hydrogen diffusion range, faster diffusion rate, higher initial kinetic energy, and are more likely to exceed the lower flammability limit of hydrogen. Q1-Turbulent Flow obstacle modeling injection process, t = 0.3 s, the gas cloud just contacted the obstacle, initially spread along the obstacle. With the continuous leakage of hydrogen, a large amount of gas comes into contact with the obstacle, and at t = 0.5 s, the obstacle starts to block the normal diffusion of leaking hydrogen, causing initial kinetic energy loss under the effect of buoyancy and obstacle blocking, and the direction of motion of hydrogen changes. When t = 0.8 s, due to the blocking effect of the obstacle wall, aggregation and vortex area are generated. t = 1 s, the area of vortex area is further increased, at this time, the degree of danger is obviously higher than before, and it is very easy to asphyxiation, explosion and other accidents.

Non-polarized and ultra-narrow band filter in MIR based on multilayer metasurface

We propose an ultra narrow-band filter in the mid infrared region (MIR) using artificial metamaterials (AMM), which is suitable for the design of on-chip photonic spectrometers. 2-D rectangular holes with a cross-like layerout are adopted to enhance the filter's efficiency and precision. Considering the penetration depth of electromagnetic (EM) waves in the metal film, we opt for multi-layer films composed of metal layers and dielectric layers, instead of a single metal layer, to improve the structure's performance in the MIR. This multilayer configuration significantly enhances the efficiency and precision of the AMM structures in the MIR. The transmission peak, with a full width at half maximum (FWHM) of 30 nm, can be achieved and tuned in the wavelength range from 3.0 μm to 10.0 μm by changing the periods of the unit cell (enlarging the unit cell from 3.0 to 10.0 μm). The proposed AMM structures, with tunable narrow band transmittance in MIR, exhibit promising potential in the fabrication of narrow band photonic detectors and on-chip spectrometers.

Multipole interference and optical sensing based on the bound states in the continuum formed in dimer metasurfaces

The all-dielectric metasurface supporting BIC based on dimer structures is proposed with the rectangular holes etched in amorphous silicon thin films. By introducing perturbations of the rotation angle of the rectangular hole as well as the difference in length and width, quasi-BIC modes in the near-infrared band can be created. Meanwhile, the research found that two different perturbations display different tuning abilities on the Fano resonance induced by the quasi-BIC. This paper reveals that the formation of the BIC mode originates from the interference between competing multipole moments, which ultimately leads to the emergence of a pair of reverse parallel electric dipoles. It explains the mismatch between the macroscopic response of the structure under the influence of competing multipole moments and the results of the multipole expansion. From the perspective of the influence of asymmetry on multipole moments, we explain the resulting radiation sources. The study demonstrates that the proposed dimer metasurface can support optical sensing under both x-polarization and circular polarization excitation, and it is observed that different perturbations have different abilities to modulate the sensitivity, which has great potential for device performance optimization and precise modulation.

Stiffness and Strength of Square Hollow Section Tubes under Localised Transverse Actions

This manuscript explores the stiffness and strength of Square Hollow Section (SHS) tubes subjected to localised transverse actions applied to the open side of a rectangular hole created using 3D laser cutting technology (3D-LCT). Understanding the behaviour of this specific detail is crucial as it is a key component in the connections between SHS columns and passing-through IPE beams. The methodology employed in this manuscript involved developing analytical equations to predict both stiffness and strength of this structural element. The provided equations are presented in a straightforward manner and were deduced by applying elasticity principles to structural components. To validate these equations, a parametric analysis was conducted, simulating the response of 27 distinct geometric configurations of the analysed structural detail thanks to the Finite Element (FE) software. Their accuracy was confirmed by comparing the results of these simulations with the outcomes derived from the formulated equations. The primary findings indicated that the proposed equations could predict the stiffness and strength of the studied detail with an average ratio close to 1 when comparing predicted and numerical results, and a coefficient of variation of approximately 10%.

Effect of Perforated Sills on Maximum Scour Depth Downstream From a Sluice Gate

Aims: Experiments were conducted to study the effect of using a perforated sill on maximum scour depth downstream from a sluice gate. Background: Previous studies have shown that screens may be utilized efficiently for dissipating the energy of water downstream of a hydraulic structure. Objective: For the present study, a series of experiments was conducted to investigate the effect of using a perforated screen sill on the maximum scour depth downstream of a hydraulic structure. Methods: In the present study, a single perforated sill with varying porosity (10.3%, 18.3%, 28.5%, and 41.1%) and an inclination angle of 90° were used. Perforated sill with different shapes of holes (circular, rectangular, and square holes) was used during the study. The major parameters for the present study are the porosity of the perforated sill, different shapes of holes, downstream water depth, and the Gate Froude number (FG) for a range covering from 2.15 to 4.7. The gate opening simulating a hydraulic structure is adjusted at heights of 4 cm, 5 cm, and 6 cm during the experiments work. Result: The results revealed that an increase in the sill porosity (Ao/As) increases the screen effect to reduce the max scour depth. In addition, the results showed that the sill with square holes is better than the sill with circular and rectangular holes in reducing the maximum scour depth. Conclusion: The perforated sill with a square porosity of 41.1% reduces the maximum scour depth downstream of a sluice gate by 60%.

Study on the effect of waveform film holes on film cooling efficiency

In order to improve the film cooling efficiency of the cooling gas on the hot side wall of the plate, the flow field, temperature field and the average film cooling efficiency of the cylindrical hole, rectangular hole and waveform hole near the wall were compared and analyzed by numerical calculation method. Compared with cylindrical holes, the average spanwise film cooling efficiency of rectangular hole is improved by 100%, and the average spanwise film cooling efficiency of waveform hole is improved by 130%. In addition, the effects of the amplitude A of the waveform hole and the initial phase ϕ on the cooling efficiency are compared and analyzed. The results show that: Within the scope of this study, when the blowing ratio M = 1, lifting the initial phase ϕ of the waveform hole can effectively improve the film cooling efficiency of the cooling gas on the wall. When the amplitude A of the waveform hole is raised, the film cooling efficiency of the cooling gas on the wall will first increase and then decrease, reaching the maximum at the amplitude A = 0.4D. At low blowing ratio, the geometric structure of waveform hole has little influence on the cooling effect of wall surface. Under high blowing ratio, when the geometric structure of waveform hole is changed, the influence of secondary flow on the average spanwise cooling efficiency of wall surface is great.

내부에 사각 홀이 있는 사각시편에서 PPS 레진의 사출성형조건에 따른 성형수축

내부에 사각 홀이 있는 사각시편에서 PPS 레진의 사출성형조건에 따른 성형수축

Numerical study of the behavior of rectangular acoustic black holes for sound absorption in air

In this work, the behavior of acoustic black holes (ABHs) serving as an anechoic termination of air-filled waveguides with a rectangular cross-section is numerically studied. These ABHs consist of a set of rigid ribs separated by narrow slits, whose height smoothly varies along the structure and whose aim is to slow-down the impinging acoustic wave and cause its absorption. For the purpose of this study, a 2D mathematical model based on linearized Navier–Stokes equations and employing the finite element method has been proposed, which allows for an accurate capturing the thermoviscous losses in the acoustic boundary layer adjacent to the solid–fluid interfaces, as well as the effects connected with geometrical details of the ABHs’ inner structure. The numerical results show that in rectangular ABHs with a fine internal structure, the acoustic wave slow-down plays a significant role and that absorption properties are strongly dependent on their inner structure details. Simplified 1D mathematical models of rectangular ABHs based on the Riccati equation or transfer matrix method have also been proposed. These simplified models are computationally highly efficient, as it has been demonstrated, they provide accurate results, especially in the case of ABHs with a fine internal structure, which feature superior acoustic energy absorbing properties.

Combined laser cutting process for interior holes in thick glasses

A novel combined laser cutting process (CLCP) has been successfully employed for the first time, as far as our knowledge extends, to enable the low-damage, high-speed cutting of interior holes in thick glass materials. To generate a precise weakening zone, a comprehensive technique utilizing the full ablation capability of a picosecond laser has been utilized. The cutting surface is split by CO2 laser-controlled crack propagation, and the final separation of the glass substrate is assisted by the temperature field. In this work, round, square, and irregular rectangular holes were cut in 6 mm soda-lime glass by CLCP. At present, the cutting speed is 150 mm/s, the minimum diameter is 60 mm, the edge chipping of two surfaces is lower than 3.5 µm and the maximum roughness of the side wall is 1.03 µm. This study proposes a new way of ultrafast laser cutting inner holes in thick glasses.

Dual-channel high sensitivity photonic crystal fiber sensor based on rectangular air holes

This paper proposes a dual-channel high sensitivity photonic crystal fiber sensor with rectangular air holes, which can detect the refractive index of a single sample or detect the refractive index of two samples simultaneously, to increase the detection efficiency and wavelength sensitivity of the sample refractive index. The sensor can reduce the times of filling, emptying and cleaning of the sample to be tested and save labor and time costs. The finite element method is used to thoroughly analyze the proposed structure’s sensing properties. The results show that when the sensor detects a single sample, the maximum wavelength sensitivity is 67,300[Formula: see text]nm/RIU, and the highest figure of merit (FOM) is 547 RIU[Formula: see text]. When the sensor detects two samples synchronously, the maximum wavelength sensitivity is 64,100[Formula: see text]nm/RIU, which is the highest level among the known sensors of the same kind. It has good application prospect in the field of high sensitivity refractive index detection.

A sonic black hole of a rectangular cross-section

In this study, a rectangular cross-section sonic black hole (SBH) is explored and a one-dimensional model equation for the acoustic field inside it is presented. The model equation's applicability is verified through a comparison with the corresponding two-dimensional Helmholtz equation. A general analytical solution, which takes into account the SBH's quadratically varying internal cross-section, is derived using linearly independent confluent Heun functions. To investigate the acoustic wave behavior in the SBH, the wave splitting method is utilized to obtain forward and backward acoustic pressure waves, and the reflection coefficient is calculated. To confirm the validity of the analytical solution, a comparison is made with numerical results obtained from the Riccati equation. Within the context of this study, a detailed discussion is provided regarding the applicability of the analytical solution.

Optimization of parameters for portable X-ray diffraction/X-ray fluorescence combined analysis device (P-XRDF-CAD)

This paper aims to optimize the parameters of a portable device that combines X-ray diffraction (XRD) and X-ray fluorescence (XRF) analysis techniques. By using the same X-ray source and detector, the device enables the simultaneous acquisition of two-dimensional XRD and XRF information from a sample with the advantage of high analysis efficiency and consistency in the measurement points. The equipment and slit materials are discussed, including the selection of the X-ray source (Moxtek MAGNUM) and the detector (Andor CCD camera). We also explore two different slit designs (the bottom-hole and side-hole) and optimize their dimensions using rectangular holes instead of inclined trapezoidal holes. Considering the fluorescence X-rays of the filters in the X-ray tube spectra, a theoretical formula is derived for rapid and accurate calculation. The calculated results are compared with the experimental results of Al and Ni filters, demonstrating good agreement across various tube voltages and filter thicknesses. Furthermore, an XRD/XRF comprehensive analysis platform is established. The effects of tube voltage, tube current, exposure time, and pixel-binning on the single-pixel events of the CCD camera are investigated and can be used to guide the selection of appropriate device parameters. The effects of the frame and tube voltage on the XRD/XRF analysis efficiency are examined for several sample materials, including Al, α-Fe, Zn, and ZrO2(Y2O3).

Terahertz meta-polarizers for simultaneous control of the amplitude, phase, and polarization

Terahertz (THz) waves hold immense potential for advancements in areas such as in 6G wireless communications, non-destructive testing, and biomedicine. However, the underdeveloped control level of THz devices has been a severe obstacle. Here, a THz meta-polarizer, comprising rectangular metallic holes, is proposed to achieve the simultaneous control of the amplitude, phase, and polarization. Each unit of this meta-polarizer can function as a miniature linear polarizer. The component polarized along the short side can pass through the unit, while the component polarized orthogonally is unable to do so. Leveraging the principles of the Malus' law, we can adjust the desired amplitude distribution of the transmitted x-polarized wave by modifying its polarization distribution. This adjustment is made possible by tuning the azimuth angle of each hole. The phase delay of the transmitted wave can be further manipulated by adjusting the hole dimensions perpendicular to the polarization direction. For given near-field amplitude distributions, the required phase distributions for generating far-field target holograms can be calculated using the Gerchberg–Saxton algorithm based on Fresnel diffraction theory. The meta-polarizer then realizes calculated phase distributions, enabling the creation of the required holograms. As a proof of concept, we designed THz meta-polarizers that can achieve two- and four-level amplitude holograms in the near field, respectively. Moreover, we also manipulated the phase distributions, allowing us to decouple the near- and far-field holograms. The experimental results agree well with the simulations. Owing to its ability to simultaneously control the phase, amplitude and polarization, the proposed THz meta-polarizer holds great application potential in 6G wireless communications, radar detection systems, and holography.

Tuberculosis detection using a low-loss and highly sensitive photonic crystal fiber technique in the terahertz regime

This research paper introduces a design and numerical investigation of a photonic crystal fiber (PCF) sensor with a hollow core. The sensor is specifically designed to detect Mycobacterium tuberculosis in the frequency range of 1–2 THz. The cladding region of the PCF sensor incorporates six rectangular air holes and an absorbing layer known as the perfectly matched layer (PML), which is utilized to examine various optical properties. Through a thorough investigation, our designed PCF sensor demonstrates enhanced sensitivity of 98.692%, 98.721%, 98.75%, and 98.764% for four different infected samples of tuberculosis at a frequency of 1.6 THz. The sensor exhibits minimal confinement loss and effective material loss. Furthermore, the numerical aperture and effective mode index of the proposed sensor are analyzed. An effective area of 346,550, 345,110, 343,710, and 343,020µm2 for the four different infected samples of tuberculosis is obtained. The fabrication methods employed for this sensor are mentioned. Overall, this PCF sensor can be promising for a wide range of chemical, gas, and biosensing applications.

An asymmetric slotted structured twin core photonic crystal fiber based highly sensitive surface plasmon resonance refractive index biosensor

A butterfly-shaped core photonic crystal fibers with less asymmetric rectangular and circular air holes are proposed, and their properties are numerically analyzed. The sensor construction is reduced to only seven air holes and uses surface plasmons stimulated inside gold (Au) strips for simplicity in manufacture and high sensitivity. Gold is employed as an effective plasmonic metal throughout this design to create resonant effects and is located away from the proposed structure to make production easier. Maximum amplitude sensitivity for the proposed sensor is 228.89 RIU−1, maximum wavelength sensitivity is 88,000 nm/RIU, and maximum wavelength resolution is 1.14 × 10−6RIU−1 for y-polarized mode where the figure of merit is 65.78 RIU−1 with a linearity of 0.9905. The proposed sensor can detect the RI of unspecified analytes between 1.27 and 1.40, allowing for the analysis of many different types of analytes, such as viruses, cancer cells, sugars, proteins, DNA/RNA and many more.

Identification of four detrimental chemicals using square-core photonic crystal fiber in the regime of THz

Numerous techniques and technologies have been proposed for the detection and identification of hazardous chemicals that can harm the lungs and respiratory system as well as the central nervous system and kidneys when inhaled. Most practical techniques can be carried out by extraordinary professionals in well-equipped facilities. A reliable, simple, highly sensitive, and feasible sensing technique is still required. A potential sensor for these harmful chemicals is the photonic crystal fiber (PCF), which achieves several unique properties. A square-core PCF sensor is proposed in this work for the detection of detrimental gases (tetra-chloro silane, tetra-chloro methane, turpentine, and tin terra-chloride) in the THz region. The cladding region is divided into three rings, and each ring has rectangular and square air holes. Within the operating region, we have found a relatively high sensitivity of 96.185% along with 95.407% core power fraction, 0.2211 numerical aperture, and a low effective area of 154 470 μm2 at 1.9 THz frequency. Ignorable confinement loss of 3.071 × 10−14 cm−1 and effective material loss of 0.007 72 cm−1 have been also found. Additionally, the current manufacturing techniques guarantee the viability of the proposed PCF sensor’s manufacture. These obtained results demonstrate that the proposed sensor can be effectively employed for applications involving hazardous chemical compounds, gases, and biosensing.

The Longest (s, t)-Path Problem on O-Shaped Supergrid Graphs

The longest (s,t)-path problem on supergrid graphs is known to be NP-complete. However, the complexity of this problem on supergrid graphs with or without holes is still unknown.In the past, we presented linear-time algorithms for solving the longest (s,t)-path problem on L-shaped and C-shaped supergrid graphs, which form subclasses of supergrid graphs without holes. In this paper, we will determine the complexity of the longest (s,t)-path problem on O-shaped supergrid graphs, which form a subclass of supergrid graphs with holes. These graphs are rectangular supergrid graphs with rectangular holes. It is worth noting that O-shaped supergrid graphs contain L-shaped and C-shaped supergrid graphs as subgraphs, but there is no inclusion relationship between them. We will propose a linear-time algorithm to solve the longest (s,t)-path problem on O-shaped supergrid graphs. The longest (s,t)-paths of O-shaped supergrid graphs have applications in calculating the minimum trace when printing hollow objects using computer embroidery machines and 3D printers.

Microparticles in One-Dimensional, Two-Dimensional and Three-Dimensional Rectangular Potential Holes

Behavior of microparticle in potential hole has been studied. One-dimensional, twodimensional and three-dimensional potential holes with infinitive deepness (with infinitively high walls) and flat bottom were observed. The stationary case was discussed. The wave function, describing the particle state, probabilities of the particle being in the given hole and its energy, depending on dimensional sizes were determined. For each case the dependencies of the wave function and its squared modulus were presented on one, two and three coordinates, respectively.

Free-form optimization of pattern shape for improving mechanical characteristics of a concentric tube

Medical concentric tubes have recently been designed using auxetic structures with negative Poisson's ratios to reduce undesirable snapping instability and improve mechanical performance. Despite the vast range of stiffness levels, prior auxetic designs were restricted to relatively simple geometries like square or triangular holes. Here, we present a novel free-form optimization for designing the bending and torsional stiffness of tubular structures using the multi-objective Bayesian optimization (MBO) method. The initial dataset of hole shapes is generated using a non-parametric Bézier curve, and the corresponding mechanical properties are estimated via numerical analysis. The acquisition function suggests a new hole shape with higher performance metrics based on the dataset, and updates to the regression model are made with new data points to improve prediction accuracy. Compared to a conventional tube with rectangular holes, the optimized design improves key factor, a ratio of bending stiffness to torsional rigidity, and torsional stiffness by 32% and 25%, respectively, by expanding the existing design space. The performance of the optimally designed tube was validated by resonant vibration tests.

Frequency domain full waveform inversion with small‐scale laboratory measurements for reconnaissance in mechanized tunneling

AbstractIn mechanized tunneling, so‐called tunnel boring machines (TBMs) drill through the ground in an automatized manner. Therefore, the drilling process is very efficient but the maintenance costs are high. Seismic exploration seems appropriate to identify changing ground conditions in front of the TBM to reduce costs from damages of the TBM and from the corresponding dwell times. Today's seismic exploration techniques are using only a small amount of the information, which is contained in the seismic records from field observations, whereas full waveform inversion (FWI) tries to use the whole content. The potential of different FWI approaches for the application in mechanized tunneling has been investigated. An analysis of the performance of FWI not only employing synthetic examples but additionally measured waveforms is essential. Since seismic surveys at the construction side are not performed with FWI in mind, the data sets are usually not appropriate for testing the developed algorithms. Nevertheless, a validation of FWI approaches by measured waveforms is possible by using waveform recordings from a small‐scale experimental setup. A small‐scale super high strength grout specimen is constructed for validating an adjoint frequency domain FWI approach. Frequency domain models compute the seismic response of a system for an infinite time interval. The attenuation of the material as well as the attenuation effects at the free surfaces are hard to quantify over an infinite time interval. Therefore, the specimen is designed in a way that four of the six borders can be modeled as absorbing boundaries. For this purpose, the displacement recordings are truncated just before the waves that are reflected at the excluded borders arrive at the measurement points. This design in combination with a notch representing a rectangular tunnel makes the measurements more similar to data from a tunnel construction side. A rectangular hole is embedded in the specimen and acts as material discontinuity, which the FWI approach is aiming to detect.