Double-layer Square Research Articles

Ultra-wideband terahertz thermal absorber with doped silicon double-layer square groove arrays

This paper introduces an ultra-wideband terahertz thermal absorber, composed of double-layer square groove doped silicon cubes, exhibiting polarization independence. Within the frequency range of 0.9–9.7 THz, the absorption efficiency exceeds 95 %, and within an incident angle range of 0–67°, the absorption rate still maintains above 90 % in the frequency range of 1.4–9.7 THz. Through finite element method (FEM), this study clearly demonstrates the distribution of electromagnetic energy within the thermal absorber and thoroughly elucidates its notable absorption efficiency via impedance matching theory. Compared to existing technologies, the proposed double-layer square groove thermal absorber shows superior performance in terms of absorption efficiency and bandwidth. This ultra-broadband terahertz thermal absorber is highly applicable in areas including biomedical imaging, thermal imaging, and wireless communication. Considering its excellent manufacturing tolerance, this thermal absorber is significant for application in real industrial production.

Energy Absorption Characteristics and Parameter Optimization of Anti-Climb Energy-Absorbing Devices for Subway Vehicles under Impact Loads

To further enhance the crashworthiness of subway vehicle anti-climb energy-absorbing devices, this paper proposes a novel collapsible structure, which is embedded with honeycomb aluminum blocks and consists of an inner and outer double-layer square tube. An impact finite element model of the subway vehicle’s anti-climb energy-absorbing device was established using LS-DYNA (v.17.2). The effects of the connecting diaphragm thickness, the inner and outer tube thicknesses of the thin-walled tubes, and the yield strength of the honeycomb aluminum on the energy absorption and impact force of the anti-climb energy-absorbing device were investigated. The results indicate that changes in the inner and outer tube thicknesses of the thin-walled tubes significantly affect the energy absorption and impact force of the anti-climb energy-absorbing device. However, changes in the connecting diaphragm thickness only increase the maximum energy absorption by up to 7.5% but have a significant impact on the maximum peak force. It was also found that the difference in energy absorption due to changes in the yield strength of the honeycomb aluminum is only 3.6%, suggesting that the yield strength of the honeycomb aluminum and the connecting diaphragm thickness have a limited influence on the crashworthiness design of the anti-climb energy-absorbing device. Furthermore, a multi-objective surrogate model characterizing the specific energy absorption and maximum peak force was established for the aforementioned four influential parameters using the response surface method. The model was then optimized using a genetic algorithm, resulting in optimal parameters that increased the energy absorption and specific energy absorption by 27.3% and 13.8%, respectively, compared to the original values, leading to a significant improvement in crashworthiness. The findings provide valuable references for and insights into the crashworthiness design and optimization of subway vehicles’ anti-climb energy-absorbing devices.

Effect of Knitting Pattern of PP Mesh on the Flexural Properties of Heat-cured PMMA Denture Base Resin

Heat-cured polymethyl methacrylate is (PMMA) is the most common denture base material and some mechanical properties such as flexural strength and impact resistance etc. may lead to fail, besides its excellent properties. Polypropylene (PP) hernia mesh is a commercially available medical textile used in surgical repair of different types of hernia. It was aimed to investigate the effect of two different knitting patterns of PP meshes on the flexural properties of the PMMA denture base resin when they are used as reinforcement and compare with glass fiber mesh reinforced and no mesh used resins. Knitting patterns of the PP mesh structures were hexagonal honeycomb pattern and square pattern and these were used as single or double layer as reinforcement. 6 groups were established in the study: control group with no mesh and 5 reinforced groups with meshes (glass fiber mesh, single layer honeycomb patterned PP mesh, double layer honeycomb patterned PP mesh, single layer square patterned PP mesh, double layer square patterned PP mesh). A total of 60 samples with the dimensions of 65x10x3 mm, n=10 in each group were fabricated. The flexural strength, maximum deformation, and flexural modulus were determined by three-point bending test. Fracture surfaces were evaluated by scanning electron microscopy. The obtained data were statistically analyzed by two-way ANOVA test with Bonferroni corrections. The single layer square patterned PP mesh group exhibited the highest (76.67 ± 7.64 MPa), and the control group showed the lowest (63.49 ± 7.18 MPa) flexural strength values. The single layer glass fiber mesh group showed the highest (7.13 ± 0.55 mm) and the control group showed the lowest (4.72 ± 0.81 mm) maximum deformation values. The single layer glass fiber mesh group exhibited the highest (2131.87 ± 205.76 MPa), and the control group exhibited the lowest (1582.26 ± 98.63 MPa) flexural modulus values. Significant increase in flexural strength was observed in all polypropylene mesh-reinforced groups compared to the control group except double layer honeycomb patterned PP mesh group (p < 0.05). Using PP fiber mesh for reinforcement provide a very favorable aesthetic view and PP fiber mesh is concluded to be a promising material for reinforcement of heat-cured PMMA denture base resins.

Numerical design of surface magneto-plasmon sensors of Au/Co double-layer square arrayed nanopores on the continuous gold thin film

Surface magneto-plasmon (SMP) sensors have attracted continuous attention due to their field enhanced signal-to-noise ratios, sensitivities, and detection limits. Although many progresses have been achieved in the nanodots, nanorods, or nanodiscs, few studies have been conducted on films containing arrays of nanopores or nanoholes. SMP sensors based on arrays of nanopores could be much more promising for future ultrasensitive optical detectors since they can couple the SMP enhancement with Fabry–Pérot interference of nanopores for high-performance resonator sensors that can be further tuned under a magnetic field. We, thus, propose a high-performance SMP sensor based on the magneto-optical Kerr effect (MOKE) of films containing a square array of Au–Co double-layer nanopores on the Au film substrate or SMP-MOKE sensor. The local electric field around the magneto-plasmon arrays of nanopore photonic crystals can be greatly enhanced by applying an external magnetic field due to their magneto-optical activity and excitation of high-quality surface plasmon resonances. Multi-physics coupling simulations and validation by COMSOL on the structure-dependent optical properties suggest that the proposed SMP-MOKE sensor has a high sensitivity of 711 nm/Refractive Index Units (RIUs) and a figure of merit (FOM) of the order of 105 RIU−1, which is an order of magnitude greater than the best grating-type sensors, to the best of our knowledge. Our results shall facilitate the theoretical design for the future fabrication of ultra-sensitive sensors or resonators with excellent FOM and reliability for air-quality monitoring or chemical sensing, etc.

First-Principles Study on Lithium Intercalation in Traditional Semiconductors Leading to Investigation of Structural Stability and Thermoelectric Properties of Their 2D Structures

In this study, we systematically investigated the lithium intercalation into nearly 30 traditional wurtzite phase semiconducting group II–VI, III–V, and IV–IV compounds. As a result, the compounds formed different structural types of layers, i.e., monolayer, bilayer, ladder-type, ribbon-type, and unexfoliated type. In addition, we correlated the reaction’s progress using each of their bulk Pauling ionic radii. After that, 20 exfoliated layers of compounds were studied. As an outcome of these calculations, they can be classified into three distinct 2D layers, which are monolayer (ML), double layer honeycomb (DLHC), and double layer square lattice (DLSL). By using the first-principles calculations to study the structural, mechanical, dynamical, electronic, and thermoelectric properties of 20 2D layers in order to determine their distinctive characteristics, our results show that most of these 2D layers are dynamically and mechanically stable. Electronic properties show that ML and DLHS structures exhibit a semiconducting nature, while the DLSL structure shows a high conducting nature. Finally, the thermoelectric behavior reveals that 20 2D layers possess outstanding figures of merit (ZT) in the range of 0.5–1.0 at 300 K, thereby they can be used as thermoelectric applications.

Study on the layout methods of stiffening rings for steel cooling towers

Stiffening rings are commonly employed as strengthening measures in steel cooling towers. However, studies on reasonable layout methods are lacking. In this study, three layout methods are proposed: the equal-spacing method, the method based on the 1st-order eigenvalue, and the method based on the 1st-order buckled mode shape. Finite element models of steel cooling towers were established considering two tower types (hyperbolic-type and cylinder-frustum-type), three tower heights (120 m, 160 m, and 200 m), three geometric parameters, and two latticed shells (single-layer rectangular and double-layer square pyramid shells). A nonlinear stability analysis of steel cooling towers designed by three layout methods was performed, and the load-bearing capacities of the structures were compared to determine the superiority and inferiority of the three layout methods. The results indicated that double-layer latticed shell steel cooling towers can satisfy the requirements of stable bearing capacity without arranging stiffening rings. The layout method based on the 1st-order buckled mode shape is more suitable than the other two methods for single-layer latticed shell steel cooling towers involving various geometric parameters. It is recommended that this method be used to design the layout of the stiffening rings.

A novel in vitro blood-brain barrier model using 3D bioprinter: A pilot study

3D bioprinters allow the creation of functional tissues using various cell lines. The blood-brain barrier (BBB) is crucial for maintaining homeostasis in the brain, acting as a protective interface between the cerebral blood vessels and the brain parenchyma. Advancements in tissue engineering have led to the development of in vitro BBB models. However, model accuracy and reproducibility still require improvements. Thus, we hypothesized that producing BBB models using a 3D bioprinter is a novel method to overcome these limitations. We tested the maintainability of habitable conditions for cells and the durability of the 3D-bioprinted BBB model. We printed four different BBB models using a bio-ink composed of Matrigel base and CPA47 endothelial cells: single- and double-layered square and circular scaffolds. The double-layered square scaffold fostered optimal BBB functions as it most effectively maintained a fixed shape and initial cell positions. When A172 glioblastoma cells were placed in the empty square spaces of the square BBB scaffold, most cells were alive and healthy after 96 hours. Although A172 cells remained in their initial cell positions until the first 48 hours, we observed movement across the Matrigel barrier when checked at 96 hours. At 48 hours, A172 cells showed no movement from their initial positions; however, by 96 hours, we observed clear movement of A172 cells across the Matrigel barrier. Due to its relative cost-effectiveness and high reproducibility, our BBB model has several applications, especially for studying brain cancer metastasis past the BBB and developing potential corresponding clinical therapeutics.

Mechanical performance of high-strength steel tube confined self-stressing concrete short columns

In this paper, eleven high-strength steel tube confined self-stressing concrete (HSTCSC) short columns were tested to study their strengthening mechanism and axial compression performance. The effects of different material strengths, cross-section types, and hollow ratios on the axial mechanical properties of the HSTCSC short columns were investigated using the finite element analysis method. Experimental results highlighted that the HSTCSC short columns presented the waist drum-type failure mode significantly, with a higher axial load-bearing capacity and deformation performance, and possess a large safety reserve. It was also found that the axial compression property of the HSTCSC short column could be improved significantly due to the joint action of the micro-expansion of the self-stressing concrete and the hoop constraint of the high-strength steel tube. Moreover, the circular cross-section HSTCSC short columns were found to result in better mechanical performance after yielding of the high-strength steel tubes, especially entering the strengthening section. Under the condition of equal steel content ratio and cross-section area, the single-layer circular HSTCSC short columns were found to have the largest load-bearing capacities after yielding the high-strength steel tubes, followed by the double-layer circular HSTCSC short columns, and then the double-layer square HSTCSC short columns. The hollow rate of the cross-section could also decrease the load-bearing capacity of the HSTCSC short column with both circular and square sections, although increasing the hollow rate could save material and reduce the weight of the structure. The finite element analysis results showed that the proposed finite element model could be employed to simulate the compressive behavior of HSTCSC short columns with high calculation accuracy.

Evolution of cooperation driven by diversity on a double-layer square lattice

Understanding the potential promotion mechanism for the formation and maintenance of cooperation is a pivotal issue in the development of human society and the natural world. Evolutionary games provide a forceful theoretical tool to probe into the essence of cooperative behaviors. It is considered that diversity (heterogeneity) is a common attribute of individuals and their interaction environment. We explore the propagation of cooperation under the influence of diversity and identify the similarities and discrepancies in the impact of internal and external sources of heterogeneity. The results show that heterogeneity, regardless of its origin, can promote the diffusion of cooperative behaviors. However, our researches further demonstrate that diversity of individual internal attributes is more conducive to the formation of cooperative behaviors than environmental heterogeneity. Moreover, we discuss the impact of asymmetry on the results and verify the robustness of the conclusions in different mixed game models. Our explorations shed some light on the promotion mechanism of cooperation from the perspective of sources of heterogeneity and highlight the role of diversity in the spread of altruistic behaviors.

Electromagnetic induction-like transparency in dual-band with dual-bright mode coupling

In this paper, a metamaterial structure with a double-layer split square ring and a double C-shaped structure is designed, which has dual-band electromagnetically induced transparency effects in the terahertz band. This structure has transmission peaks at 1.438 THz and 1.699 THz. Through the analysis of the surface current distribution, the reasons for the dual-band electromagnetically induced transparency are discussed. The effect of the designed metamaterial on the transmission window is studied when the opening size of the open square ring and the distance of the double C-shaped structure and the incident angle are changed. At an incident angle, the transmission spectrum of the designed material changes greatly, implying that it is highly sensitive to angle. The research results show that the structure has potential applications in sensors and angle filters.

Ultralight micro-perforated sandwich panel with double-layer hierarchical square honeycomb core for broadband sound absorption

The micro-perforated panel (MPP) has only one sound absorption peak, and the sound absorption performance is poor in the wide frequency range. Besides, the stiffness and strength of MPP are insufficient, so it can not bear the external load. In this study, double layers of hierarchical square honeycomb are placed within the air-back cavity of MPP to produce a sandwich structure. On the one hand, hierarchical honeycombs divide the air-back cavity into several sub-cavities. The perforations on the panel together with the sub-cavities form a series-parallel system of Helmholtz resonators. The sound absorption curve of the structure has multiple peaks and the half-absorption bandwidth is extensively widened. On the other hand, the hierarchical honeycomb with excellent load-bearing properties can strongly support the MPP to resist external loads. This new structure possesses both sound absorption and load bearing capabilities, and has practical application value in the noise reduction of high-speed trains and civil aircraft. Through theoretical and simulation analysis, the sound absorption performance of the structure is systematically studied and the influence of key parameters is quantified, providing guidance for the design of noise reduction materials.

Dynamic Structural Evolution of Mn–Au Alloy and MnOx Nanostructures on Au(111) under Different Atmospheres

Construction of inverse oxide/metal model catalyst with specific chemical composition and interfacial structure is essential for clarifying their structure–performance relationship. This work describes the structural evolution of Mn–Au surface alloy and two-dimensional manganese oxide (MnOx) islands on Au(111) surface under different treatment conditions. By employing near-ambient pressure scanning tunneling microscopy and X-ray photoelectron spectroscopy, we can obtain four different MnOx structures. Among them, double-layer square lattice Mn3O4(001) and monolayer parallelogram-shaped Mn3O4 are prepared by postannealing Mn–Au surface alloy in “oxygen-poor” and “oxygen-rich” regimes, respectively. Annealing the monolayer parallelogram-shaped Mn3O4 in vacuum to 700 K produces a double-layer structure consisting of Mn3O4 top layer and MnO(111) bottom layer, while double-layer MnO(111) is formed after annealing in vacuum to 800 K. Our study lays the foundation for exploring the catalytic properties of inverse manganese oxide/metal model catalysts.

Study and Design of Single and Double Layer Square Patch Antennas for UWB Applications

This paper presents the design of Single and Double Layer microstrip patch antennas for ultra-wideband applications. This structure consists of a square patch with a partial ground plane, fed by a 50[Formula: see text][Formula: see text] microstrip line. This antenna is designed for a system to detect malignant tumors by microwave imaging. Prototypes of the two antennas are fabricated and tested with a network analyzer. The proposed antenna can achieve an ultra-wide bandwidth with VSWR[Formula: see text]2 from 3.82[Formula: see text]GHz to 11.72[Formula: see text]GHz for single layer antenna and from 3.2[Formula: see text]GHz to 10.95[Formula: see text]GHz for double layer antenna, with stable and bi-directional radiation pattern. The gain is good and has a peak value of 6.5[Formula: see text]dBi. The simulation of this antenna has been performed using Ansoft High Frequency Structure Simulator (HFSS) and Computer Simulation Technology-Microwave Studio (CST).

Double-layer ice from first principles

The formation of monolayer and multilayer ice with a square lattice structure has recently been reported on the basis of transmission electron microscopy experiments, renewing interest in confined two-dimensional ice. Here we report a systematic density functional theory study of double-layer ice in nanoconfinement. A phase diagram as a function of confinement width and lateral pressure is presented. Included in the phase diagram are honeycomb hexagonal, square-tube, hexagonal-close-packed, and buckled-rhombic structures. However, contrary to experimental observations, square structures do not feature: our most stable double-layer square structure is predicted to be metastable. This study provides general insight into the phase transitions of double-layer confined ice and a fresh theoretical perspective on the stability of square ice in graphene nanocapillary experiments.

Circuit Model of a Double-Layer Artificial Magnetic Conductor

This letter presents a circuit model to design a double-layer square artificial magnetic conductor (AMC) with a small period relative to the wavelength in the UHF band. The miniaturization is achieved thanks to a square patch array printed alternatively on each side of a thin dielectric substrate. These closely spaced arrays cause a high grid impedance allowing to decrease the period of the AMC. The proposed model is validated by simulations for several configurations and by measurements. The resonance frequency of the realized AMC is 2.68 GHz with a bandwidth of 260 MHz. The dimensions of the unit cell are $ 11.5 \times 11.5~\hbox{mm}^2$ or $0.1{\lambda _0} \times 0.1{\lambda _0}$ .

A circularly polarized slot antenna for high gain applications

A coplanar waveguide fed slot antenna for wideband circular polarization is designed and experimentally validated. The rectangular slot is excited using a stepped feed line terminated on a circular disc shaped tuning stub. To obtain circular polarization, inverted L-shaped strips are attached to the ground plane at the opposite corners while a rectangular slit is cut in the circular disc. The combined bandwidth (3-dB axial ratio and 10dB impedance matching) achieved is 48% (4.35–7.1GHz) under simulation and 40% (4.75–7.1GHz) in measurement. The gain of the antenna is next enhanced by the application of a double layered square loop frequency selective surface. The frequency selective surface is used as a reflector placed beneath the antenna at an optimum distance. An improvement of about 4dB is seen in the measured peak gain over most of the operating band. Experimental results are presented to characterize the antenna and the frequency selective surface and they are found to be in good agreement with the simulated results.

The Fire Resistance Performance of Double-Layer Square Pyramid Silo-Shell Structure under Fire

With fire temperature rising, elastic modulus of steel would be reduce, which then would lead to global instability phenomenon of double-layer square pyramid silo-shell structure. In order to analyze its fire resistance performance under high fire temperature, different geometric parameters were set based on the effect factors when it operated normally at room temperature. To analyze its displacement change by conducting nonlinear finite element analysis which was under the two typical temperature rising cases including global non-uniform temperature and localized high temperature. Then, with the temperature rising, the fire resistance performance and the maxium displacement changing rule were obtained.

A new hybrid desalination system using wicks/solar still and evacuated solar water heater

This paper presents a new hybrid desalination approach comprising of evacuated solar water heater, jut geotextile and solar still. An evacuated solar water heater is integrated with the desalination stills to evaluate the continuity production of distillate. Two identical portable solar wick and one basin solar stills were designed to evaluate the systems performance. Jut linen woven fabrics were stitched to the plane wick (lengthwise and crosswise) and integrated with solar still. The jut fabrics were used to reduce the rate of water flow to the appropriate rate. The following variables are studied: Single and double layers wick; plane wick, lengthwise and crosswise linen; feeding hot water during night and two base slope angles of wick still (20 and 30°). Theoretical analysis is verified through experiments. Water productivity is increased by 114% over conventional still for double layer square wick (DLSW) solar still at 30° base slope angle. The daily average efficiency of DLSW was 71.5%. During experimentation, the distillate water productivity increased by 215% when hot brackish water was fed during night time.

Syntheses, structures and characteristics of four metal–organic coordination polymers based on 5-hydroxyisophthalic acid and N-containing auxiliary ligands

Solvothermal reactions of 5-hydroxyisophthalic acid (hip) and different N-containing auxiliary ligands with transition metal salts provided four new metal–organic coordination polymers (MOPs), namely, {Zn(hip)(2,2′-bipy)·2H2O}n (1), {[Ni(hip)(4,4′-bipy)(H2O)]·DMF·2H2O}n (2), {Zn(hip)(tib)·2H2O}n (3), {[Zn2(hip)2]·5H2O}n (4), (2,2′-bipy = 2,2′-bipyridine, 4,4′-bipy = 4,4′-bipyridine, DMF = N,N′-dimethylformamide, tib = 1,3,5-tris(1-imidazolyl)benzene). All of the complexes have been structurally characterized by single-crystal X-ray diffraction analyses, infrared spectra (IR), elemental analyses and powder X-ray diffraction (PXRD). Single crystal X-ray diffraction analysis reveals that complex 1 exhibits a one-dimensional zig-zag chain, in which strong π⋯π interactions are found between neighbouring 2,2′-bipy molecules. Complex 2 has a 2D double-layer square framework, exhibiting AA stacking sequence, and the topology of each layer is typical 2D (44)-sql. In complex 3, both hip and tripodal ligand tib act as bidentate bridging ligand and extend the tetragonal pyramid Zn(II) centers to a 2D wavy framework, exhibiting an AB stacking sequence. The 2D layer structures in 2 and 3 are different from each other. In complex 4, the oxygen atoms of the hydroxy group of hip participate in constructing a framework, which results to the 3D net framework with 1D channel. The structural and topological differences of the four MOPs indicate that the auxiliary ligand play important roles in the formation of final structures. Furthermore, the thermal stability and photoluminescence properties of complexes 1–4 were investigated.

Effects of van der Waals interactions on the nonlinear vibration of multi-layered graphene sheets

This paper is concerned with the forced nonlinear vibration of multi-layered graphene sheets modelled at the atomic level by the lattice structure approach. In this, the covalent bond between two carbon atoms is assumed as a structural member with prescribed physical and material properties. An atom is treated as a nodal point with its own mass and six degrees of freedom. The highly nonlinear van der Waals interaction between adjacent graphene layers is fully incorporated in the model by placing it in the force vector. This adjustment significantly reduces the computational hardships due to nonlinearity and increases the efficiency of the method. Newmark's direct integration method is modified to address the nonlinearity in the load vector and used for the solution of the matrix equation governing the motion of the multi-layered graphene sheet. Double-layered square graphene with simply supported and clamped boundary conditions is analysed to examine the out-of-plane and in-plane vibrational characteristics. Also, in order to illustrate the applicability of the numerical method, analyses are carried out with the first- and second-order Taylor series approximations of the van der Waals interactions, influence of which is found to be quite significant in the bending modes of vibration, but it essentially does not have a role in the in-plane modes. The numerical method developed herein is quite appropriate with reference to the structural formation at the atomic scale and also more efficient than previous computational approaches by others.